HP Continuous Access Journal Z User Manual

HP StorageWorks
P9000 Continuous Access Journal for
Mainframe Systems User Guide

Abstract

This guide explains how to use HP StorageWorks P9000 Continuous Access Journal for Mainframe Software to replicate data
between local and remote HP StorageWorks P9000 disk arrays and to achieve disaster tolerance with maximum application
performance. Topics include setting up remote copy connections, configuring the storage system, creating and monitoring
remote copies, recovering from a disaster, and troubleshooting. The intended audience is a storage system administrator or
authorized service provider with independent knowledge of HP StorageWorks P9000 disk arrays and the HP StorageWorks
Remote Web Console.

HP Part Number: AV400-96397
Published: September 2011
Edition: Fifth

© Copyright 2010, 2011 Hewlett-Packard Development Company, L.P.

Confidential computer software. Valid license from HP required for possession, use or copying. Consistent with FAR 12.211 and 12.212, Commercial
Computer Software, Computer Software Documentation, and Technical Data for Commercial Items are licensed to the U.S. Government under
vendor's standard commercial license.

The information contained herein is subject to change without notice. The only warranties for HP products and services are set forth in the express
warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shall
not be liable for technical or editorial errors or omissions contained herein.

Acknowledgements

Microsoft®, Windows®, Windows® XP, and Windows NT® are U.S. registered trademarks of Microsoft Corporation.

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Revision History

DescriptionDateEdition

Applies to microcode version 70-01-01-00/00 or later.October 2010First

Applies to microcode version 70-01-24-00/00 or later.November 2010Second

Applies to microcode version 70-01-62-00/00 or later.January 2011Third

Applies to microcode version 70-02-01-00/00 or later.May 2011Fourth

Applies to microcode version 70-02-5x-00/00 or later.September 2011Fifth

Contents

1 Continuous Access Journal Z overview ..........................................................8

Continuous Access Journal Z software ........................................................................................8

How Continuous Access Journal Z works.....................................................................................8

Hardware and software components...........................................................................................9

P9500 storage systems.......................................................................................................10

Main and remote control units .......................................................................................11

Pair volumes......................................................................................................................11

Journal volumes.................................................................................................................11

Journals............................................................................................................................11

Data path.........................................................................................................................12

Extended consistency groups...............................................................................................12

Remote Web Console ........................................................................................................12

Business Continuity Manager..............................................................................................13

Overview of copy operations...................................................................................................13

Initial copy operation.........................................................................................................13

Update copy operation ......................................................................................................14

Read and Write I/O operations during remote copy operation.....................................................15

S-VOL write option..................................................................................................................15

S-VOL read option..................................................................................................................15

Difference management...........................................................................................................15

Pair status..............................................................................................................................16

2 Requirements and specifications.................................................................17

System requirements................................................................................................................17

Business Continuity Manager specifications ...............................................................................19

Command device ..................................................................................................................21

3 Planning volumes, systems.........................................................................22

Plan and design workflow .......................................................................................................22

Assessing business requirements for data recovery......................................................................22

Determining your RPO........................................................................................................23

Write-workload......................................................................................................................23

Measuring write-workload...................................................................................................23

Sizing journal volumes............................................................................................................24

Determine the required journal volume capacity.....................................................................24

Calculating the journal size.................................................................................................25

Planning journals...............................................................................................................25

Data transfer speed considerations...........................................................................................26

RAID group configuration....................................................................................................26

Fibre Channel port configuration..........................................................................................26

Planning journal volumes.........................................................................................................26

Host I/O time stamp..........................................................................................................27

Planning pair volumes.............................................................................................................27

Data and journal volume specifications.................................................................................27

Duplicating VOLSERs..........................................................................................................28

Maximum number of pairs allowed .....................................................................................29

Calculating maximum number of pairs.............................................................................29

Priority set for initial copy operations and scheduling order.....................................................30

Disaster recovery considerations ..............................................................................................31

Error reporting communications (ERC)...................................................................................32

Sharing volumes with Continuous Access Synchronous Z, other program products...........................32

Planning for Continuous Access Journal Z with multiple P9500 systems..........................................32

Contents 3

Establishing connections between multiple secondary systems..................................................34

Planning extended consistency groups (EXCTG).....................................................................34

Planning for previous models ...................................................................................................35

Guidelines for preparing systems for Continuous Access Journal Z.................................................36

System option modes..........................................................................................................36

4 Planning the data path..............................................................................39

Data path design workflow .....................................................................................................39

Sizing bandwidth ..................................................................................................................39

Five sizing strategies ..........................................................................................................39

Calculating bandwidth ......................................................................................................40

Sizing bandwidth for peak write-workload........................................................................40

Sizing bandwidth for peak rolling average write-workload..................................................41

Latency .......................................................................................................................42

Packet loss ...................................................................................................................42

Planning ports for data transfer ................................................................................................43

Determining required number of ports ..................................................................................43

On setting up ports ...........................................................................................................44

Distances supported for Fibre Channel type, number of switches ..................................................44

Supported data path configurations .........................................................................................45

5 Using extended consistency groups.............................................................47

Overview .............................................................................................................................47

Register journals in an EXCTG .................................................................................................49

Split, restore, release pairs in an EXCTG ...................................................................................50

Pair-split operation.............................................................................................................50

Operations for a specific journal .........................................................................................50

Remove journals from an EXCTG ..............................................................................................51

Forcibly remove journals.....................................................................................................52

Using EXCTGs with P9500.......................................................................................................52

6 Configuration operations...........................................................................55

Configuration workflow ..........................................................................................................55

Define Fibre Channel port attributes .........................................................................................55

Configure storage systems for Continuous Access Journal Z, define logical paths ............................57

Configure additional logical paths ...........................................................................................59

Specify number of volumes for initial copy, resync ......................................................................60

Register journal volumes in a journal.........................................................................................62

7 Pair operations.........................................................................................66

Pair operations workflow.........................................................................................................66

Check pair status....................................................................................................................66

Create the initial copy ............................................................................................................66

Split a pair ...........................................................................................................................70

Split a mirror..........................................................................................................................72

Create a point-in-time copy .....................................................................................................72

Restore a pair........................................................................................................................73

Resynchronize a mirror............................................................................................................75

Delete a pair ........................................................................................................................76

Delete pair volumes from a mirror.............................................................................................78

8 Monitoring the system...............................................................................79

Monitor pair activity, status......................................................................................................79

Pair status definitions..........................................................................................................79

Suspend types..............................................................................................................82

Suspension conditions from the secondary system..............................................................83

Filtering Information in the List in the Pair Operation window...............................................84

4 Contents

Saving pair status information into a text file.....................................................................85

Monitor copy operations data, I/O .....................................................................................86

Select data to be graphed..............................................................................................87

Manipulate graph, save data..........................................................................................89

Monitor journal status..............................................................................................................89

Mirror Journal status definitions............................................................................................89

Monitor logical path status.......................................................................................................90

History of operations for data volume pairs...........................................................................91

9 Maintaining the system ............................................................................92

Pair maintenance—change the pair-split option .........................................................................92

Journal and mirror maintenance...............................................................................................93

Change Continuous Access Journal Z options used by journals................................................93

Change Continuous Access Journal Z options used by mirrors .................................................95

Delete journal volumes from a journal...................................................................................97

Delete a journal.................................................................................................................98

Logical path maintenance........................................................................................................98

Modify data-transfer time threshold .....................................................................................98

Delete logical paths ..........................................................................................................99

Delete the Continuous Access Journal Z relationship ............................................................100

Manage power-off for systems and network devices .................................................................100

When power stops unexpectedly.......................................................................................100

When power is removed from primary or secondary system..............................................100

When power is removed from network relay devices .......................................................101

Power-off storage systems intentionally................................................................................101

Power-off the primary or secondary system......................................................................101

Power-off primary and secondary systems at the same time...............................................101

Power-off network relay devices..........................................................................................102

10 Disaster recovery operations ..................................................................103

Preparing for disaster recovery ..............................................................................................103

File and database recovery procedures ..................................................................................103

Switch operations to the secondary site ..................................................................................103

Copy data back to the primary site ........................................................................................104

Resume normal operations at the primary site ..........................................................................104

Disaster recovery for multiple primary and secondary storage systems.........................................105

Consistency of data update sequence when a disaster occurs................................................105

Disaster recovery for multiple primary and secondary storage systems....................................105

Recovery procedures with shared volumes................................................................................105

Recovery in a 3DC cascade configuration ..........................................................................106

Transferring business tasks back to the primary site..........................................................106

Recovering from primary site disaster in 3DC multi target configuration...................................107

Recovering from primary site failures (when delta resync operation is performed)......................109

Recovering from failures in the primary site and the Continuous Access Synchronous Z secondary

site................................................................................................................................112

Recovery with Business Copy Z configuration ......................................................................113

11 Troubleshooting....................................................................................114

General troubleshooting........................................................................................................114

Troubleshooting logical paths ................................................................................................115

Troubleshooting suspended pairs ...........................................................................................117

Troubleshooting using Remote Web Console............................................................................118

Error codes .........................................................................................................................119

Service information messages (SIMs) ......................................................................................119

Enabling or disabling SIM reporting...................................................................................121

Clearing SIMs.................................................................................................................122

Contents 5

12 Support and other resources...................................................................123

Contacting HP......................................................................................................................123

Subscription service..........................................................................................................123

Documentation feedback..................................................................................................123

Related information...............................................................................................................123

HP websites....................................................................................................................124

Conventions for storage capacity values..................................................................................124

Typographic conventions.......................................................................................................124

A Sharing Continuous Access Journal Z volumes ...........................................126

Volume types that can be shared with Continuous Access Journal Z.............................................126

Virtual LVI ...........................................................................................................................128

Cache Residency..................................................................................................................128

Auto LUN............................................................................................................................128

Performance Monitor ............................................................................................................128

Data Retention.....................................................................................................................129

B Continuous Access Journal Z configurations with Continuous Access Synchronous

Z.............................................................................................................130

Sharing volumes with Continuous Access Synchronous Z............................................................130

3 data center cascade configuration.......................................................................................130

Prerequisite information for 3DC cascade ...........................................................................131

Procedure for setting up 3DC cascade ...............................................................................132

3 data center multitarget configuration ...................................................................................132

Prerequisite information for 3DC multitarget.........................................................................133

Procedure for setting up 3DC multitarget.............................................................................133

Delta resync configuration .....................................................................................................134

Prerequisite information for creating the delta resync pair......................................................135

Prerequisite information for performing delta resync operation................................................135

Procedure for creating a delta resync pair ..........................................................................136

Configuring delta resync operation environment to support remote command devices................137

Establish immediate communications ............................................................................137

Assign mirrors to remote command devices ....................................................................138

Release mirrors...........................................................................................................139

Perform the delta resync operation .....................................................................................140

C Continuous Access Journal Z configurations with Business Copy Z................141

Overview............................................................................................................................141

Configurations with Business Copy Z primary volumes ..............................................................141

Configurations with Business Copy Z secondary volumes ..........................................................143

Pair status and data currency.................................................................................................143

Using At-Time Split function when combining Continuous Access Journal Z with Business Copy Z....144

D Continuous Access Journal Z GUI reference...............................................147

Journal Operation window ....................................................................................................147

Journal Detail window ..........................................................................................................150

Change Journal Option dialog box ........................................................................................153

Change Mirror Option dialog box .........................................................................................154

Edit Journal Volumes dialog box.............................................................................................155

Pair Operation window ........................................................................................................156

Detailed Information dialog box ........................................................................................160

Add Pair dialog box ........................................................................................................163

Suspend Pair dialog box ..................................................................................................166

Resume dialog box .........................................................................................................167

Delete Pair dialog box .....................................................................................................168

Change Pair Option dialog box.........................................................................................169

6 Contents

Display Filter dialog box ..................................................................................................169

DKC Operation window .......................................................................................................170

Remote Systems Information ..............................................................................................172

Logical Path Information....................................................................................................173

Port Information for the local system....................................................................................173

DKC Status dialog box ....................................................................................................174

Add DKC dialog box .......................................................................................................176

DKC Option dialog box ...................................................................................................177

Usage Monitor window ........................................................................................................178

History window ...................................................................................................................178

Operations in History window ..........................................................................................180

History window notes.......................................................................................................181

Export operations history .................................................................................................182

Optional Operation window .................................................................................................182

EXCTG Operation window ....................................................................................................183

View the EXCTG List ........................................................................................................185

View Storage Systems in an EXCTG ...................................................................................186

View journals in an EXCTG ..............................................................................................186

Add Journal....................................................................................................................187

Glossary..................................................................................................189

Index.......................................................................................................191

Contents 7

1 Continuous Access Journal Z overview

Unless otherwise specified, the term P9000 in this guide refers to the following disk array:

• P9500 Disk Array

The GUI illustrations in this guide were created using a Windows computer with the Internet Explorer
browser. Actual windows may differ depending on the operating system and browser used. GUI
contents also vary with licensed program products, storage system models, and firmware versions.

With Continuous Access Journal Z (Cnt Ac-J Z), you create and maintain a remote copy of a data
volume on a P9500 system. The remote copy is a block-for-block copy of the local storage volume.
Remote data is consistent with local data and therefore available for recovery of the local volume
should the need arise.

This guide provides instructions for planning, implementing, operating, maintaining, and
troubleshooting a Continuous Access Journal Z system.

The following configurations described in this document are unsupported in version 70-01-0x.

• Three data center (3DC) multitarget configuration

• Three data center (3DC) cascading configuration

• Three data center (3DC) configuration using the delta resync function

• Configuration using multiple primary and secondary storage systems

Continuous Access Journal Z software

With Continuous Access Journal Z, application data is copied to a secondary P9500 system at a
remote location. Continuous Access Journal Z is designed to support a remote site hundreds and
even thousands of miles from the local site, making recovery from region-wide disasters possible.
This guide provides scenarios and procedures for disaster recovery from multiple sites.

When a pair is created, the remote system will contain an asynchronous, block-for-block copy of
the local storage volume. Impact on host I/O and the primary storage system is limited, since
updates sent to the primary volume are also copied to a local journal volume. The remote system
“pulls” data from the journal volume across the communication link to the backup-volume. The
primary system is free to perform its role as a transaction processing resource rather than as
replication engine.

How Continuous Access Journal Z works

With Continuous Access Journal Z, you enable a data back up from a primary volume (P-VOL) on
the local system to a secondary volume (S-VOL) on a remote system. Continuous Access Journal Z
operations are performed sequentially as shown below.

Figure 1 Basic sequence in Continuous Access Journal Z operations

8 Continuous Access Journal Z overview

Remote replication occurs using journal volumes on the local and remote systems.

• The journal on the local system is the “master journal.”

• The journal on the remote system is the “restore journal.”

Replication occurs in the following sequence:

• Journal obtain - When the host sends an update to the primary volume, the system’s

journal-obtain function triggers a copy of the update data to the master journal volume.

◦ The host assigns write-sequence numbers to the data sent to the journal.
◦ Write-sequence numbers and other metadata attached to journal data insure consistency

with the data in the primary volume.

• Journal copy - data is copied from the master journal to the restore journal.

If the master journal has data, the primary system transfers it to the restore journal. When
data transfer is complete, master journal data is discarded.

◦

◦ Data copy to the restore journal is initiated by the read-journal command issued by the

remote system.

◦ Data copy occurs on a continual basis unless there is no data in the local journal. On

the remote storage system, journal reading operations are performed just after finished
the former read operation.

• Journal-restore - the secondary volume is updated with changed data from the restore journal.

Data is copied to the secondary volume according to the write sequence numbers, insuring
data consistency.

◦

◦ When journal-restore is completed, the data in the restore journal is discarded.
◦ In the configuration of Continuous Access Journal Z, the updating of data volumes and

the creating of journal data are processed. Therefore, the performance decreases
compared with the configuration only of data volumes, and usage rates rise in the
configuration of Continuous Access Journal Z.

◦ The primary storage system does not remove the target journal data from its master journal

volume until it receives the sequence numbers of the restored journal that is given to the
read journal command from the secondary storage system. This is true even if the primary
storage system and secondary storage system are connected using a channel extender
product.

Hardware and software components

A typical configuration consists of a P9500 or externally attached system on both local and remote
sites, a host or hosts connected to the systems, Continuous Access Journal Z software on both
systems, data path connections, and interface tools for configuring and managing Continuous
Access Journal Z.

• The local and remote P9500 systems are connected using dedicated fibre channel data paths,

which can include fibre channel switches. Data paths are routed from the fibre channel ports
on primary system to the ports on the secondary system.

• The host is connected to the P9500 using a FICON channel port.

• Remote Web Console is connected via a management LAN.

Hardware and software components 9

A Continuous Access Journal Z system consists of the following:

• P-VOLs and S-VOLs on the local and remote P9500

• Master and restore journal volumes on the local and remote P9500

• Master and restore journals on the local and remote P9500

The master journal consists of the primary volume(s) and master journal volume(s).◦

◦ The restore journal consists of the secondary volume(s) and restore journal volume(s).

When Continuous Access Journal Z journals consist of journal volumes located in multiple systems,
a host I/O time stamping function is required. This is provided by MVS DFSMSdfp.

An error reporting communications (ERC) feature is also required when Continuous Access Journal
Z is to be used for disaster recovery.

Management software consists of:

• Remote Web Console graphical user interface (GUI)

• Business Continuity Manager

• Configuration File Loader

NOTE:

• Continuous Access Journal Z processing continues uninterrupted if the SVP reboots or even if

the SVP fails.

• Continuous Access Journal Z does not support operations in which one P-VOL is copied to

more than one S-VOL, or more than one P-VOL is copied to one S-VOL.

Continuous Access Journal Z components are illustrated in the following figure and described in
greater detail in the following sections.

Figure 2 Continuous Access Journal Z components

P9500 storage systems

Continuous Access Journal Z is operated using two P9500 storage systems, one at the primary
and one at secondary sites. The primary system consists of the main control unit (MCU) and the
SVP . The secondary system consists of the remote control unit (RCU) and the SVP.

• The primary system communicates with the secondary system over dedicated fibre channel

remote copy connections.

• The P9500 system can function simultaneously as a primary and secondary system.

10 Continuous Access Journal Z overview

Main and remote control units

The primary and secondary systems are often referred to as the MCU (primary system) and RCU
(secondary system). MCU is the main control unit, RCU is the remote control unit.

MCUs control the primary storage volume (P-VOL) and the following operations:

• Host I/O operations to the P-VOL

• Master journal operations

• Initial copy and update copy operations between the P-VOL and secondary volume (S-VOL).

RCUs control the secondary storage volume (S-VOL) and the following operations:

• Issue read-journal commands to the MCU.

• Manage the copying of journal data from master to restore journal

• Manage the copying of restore journal data to S-VOL

• Assist in managing pair status and configuration (for example, rejects write I/Os to the S-VOLs).

Pair volumes

Original data is stored in the P-VOL and the remote copy is stored in the S-VOL. The pair can be
paired, split, resynchronized, and returned to the simplex state. When synchronized, the volumes
are paired; when split, new data sent is to the P-VOL but held from the S-VOL. When resynchronized,
changed data is copied to the S-VOL. When a disaster occurs, production operations can be
transferred to the S-VOL. When the primary site is functional again, operations and data can be
transferred and copied back to the P-VOL.

The P-VOL remains available to the host for read and write I/O operations. The secondary system
rejects write I/Os for the S-VOL, unless the write-enable option is specified for the S-VOL. Then,
write I/O is allowed to the S-VOL while the pair is split. In this instance, S-VOL and P-VOL track
maps keep track of differential data and uses it to resynchronize the pair.

See “Duplicating VOLSERs” (page 28) for further information on volume requirements and support.

NOTE: When you configure a journal pair, you have to specify the serial numbers of primary

storage systems and secondary storage systems. You have to specify the different serial numbers
of the primary storage system and the secondary storage system for the same journal pair. If you
have to specify the same serial number, contact HP Technical Support.

Journal volumes

Journal volumes are required on the primary and secondary systems.

• Updates to the P-VOL are copied to the master journal volume in the primary system. See the

illustration in “Journals” (page 11).

• Master journal data is copied to the restore journal volume on the secondary system.

• Journal volumes can have different volume sizes and different RAID configurations.

• Journal data is stored sequentially and separately into each journal volume in the same journal.

For information on planning journal volumes, see “Sizing journal volumes” (page 24).

NOTE: If a path is defined from a host to a volume, you cannot register the volume as a journal

volume.

Journals

Journals help you manage data consistency between multiple P-VOLs and S-VOLs. A journal consists
of two or more data volumes and journal volumes.

Hardware and software components 11

You use journals to create multiple pairs and to split, resync, and release multiple pairs. Journals
are required on the primary and secondary systems.

Each data volume and its associated journal volume reside in the same journal. This is illustrated
below.

• The master journal group contains master journal volumes and is associated with the P-VOL.

• The restore journal group contains restore journal volumes and is associated with the S-VOL

Each pair relationship between journals is called a "Mirror". A Mirror ID identifies a pair relationship
between journal groups. When the pair is created, it is assigned a mirror ID.

Figure 3 Journal Groups

Data path

The physical transmission link between the local and remote systems is called the data path.
Continuous Access Journal Z commands and data are transmitted through the fibre channel data
path and switches. The data path is connected to the primary and secondary systems through two
types of Fibre Channel ports, Initiator and RCU Target ports.

One data path connection is required for Continuous Access Journal Z. HP recommends two or
more independent connections to provide hardware redundancy. A maximum of eight paths can
be used.

For more information, see ???.

Extended consistency groups

To maintain data consistency when performing copy operations between multiple primary systems
and multiple secondary systems, the associated journals must be registered in an extended
consistency group (EXCTG). An EXCTG is a collection of journals in which data consistency is
guaranteed. See “Planning extended consistency groups (EXCTG)” (page 34) for more information.

Remote Web Console

Remote Web Console communicates with the SVP of each storage system over defined TCP/IP
connections.

• Remote Web Console must be LAN-attached to the primary system

• Remote Web Console is not required on the secondary system; however having it available

allows you to change Continuous Access Journal Z parameters and access the Continuous
Access Journal Z S-VOL for maintenance or disaster recovery.

12 Continuous Access Journal Z overview

NOTE:

• Storage Administrator (Remote Copy) role access to the Remote Web Console Java applet

program is required to perform operations. Users without Storage (Remote Copy) role write
access can only view (Remote Copy) role information.

• If the RAID Manager computer is not installed, contact HP Technical Support for information

on Continuous Access Journal Z configuration services.

Business Continuity Manager

Business Continuity Manager provides management of Continuous Access Journal Z software in
mainframe environments. Business Continuity Manager software automates Continuous Access
Journal Z operations (as well as operations for Business Copy Z and Continuous Access Synchronous
Z). Access to system performance metrics and thresholds provides problem avoidance and optimum
performance.

Overview of copy operations

The following sections describe initial and update copy operations including the underlying
operations, such as journal processing and differential data management.

Initial copy operation

The initial copy is executed when the primary storage system copies all the data in sequence in
the P-VOL directly to the S-VOL. Though journal volumes are not used during the initial copy, the
copy data in this operation is referred to as “base journal data.”

• Creating pairs independently of journal activity results in the base journal data being copied

to the respective S-VOLs one at a time. This extends the time required for multiple initial copies.

• An initial copy operation can be performed to establish the Continuous Access Journal Z pair

relationship — with no data copied between the volumes. This can be done when data in the
P-VOLs and S-VOLs are the same.

• A volume pair can also be created using a Continuous Access Synchronous initial copy

operation. See “Planning pair volumes” (page 27) for more information.

Overview of copy operations 13

NOTE:

• If you manipulate volumes (not journals) to create or resynchronize two or more data volume

pairs within the same journal, the base journal of one of the pairs is stored in the restore
journal volume. Then, the base journal of another pair is stored in the restore journal volume.
Therefore, the operation for restoring the latter base journal is delayed.

• You can specify None as the copy mode for initial copy operations. If the None is specified,

initial copy operations are not performed. Therefore, if you specify None, you are responsible
for ensuring that the data in the primary and secondary data volume is completely the same.

• You may create a Continuous Access Journal Z data volume pair by using Continuous Access

Synchronous Z initial copy. In that case, set the appropriate system option that is system option
474, on both primary and secondary storage system. In addition, the script, which is written
especially for this operation, is also required. If you use the script without setting the system
option on the secondary storage system, the storage system recognizes the Continuous Access
Synchronous Z R-VOL as the Continuous Access Journal Z S-VOL, and the SSB log (SSB=CBED)
is generated in the secondary storage system. In this case, the command to create the pair is
rejected. The script is executed normally when you use the script without setting the system
option on the primary storage system, however, note that the processing speed of the
Continuous Access Synchronous Z initial copy slows down if there is the update I/O during
the operation.

• If you delete all Continuous Access Journal Z data volume pairs in the journal and then create

a Continuous Access Journal Z data volume pair, wait for one or more minutes after deleting
pairs.

• When an RCU is shared with multiple MCUs, perform the pair resume operation after system

option mode 593 is set to available if you resume 1025 or more pairs from multiple MCUs
(range: mirror) at the same time. Pair resume operations may fail if system option mode 593
is not available.

Update copy operation

When a host produces new or changed information, the following occurs in the primary storage
system:

• The update is written to the P-VOL

• The update is copied to the master journal along with metadata that includes sequence and

other consistency information.
Replication to the secondary system is prompted by the read-journal command. This is issued

by the remote system independently of host I/O activity. Read-journal commands are repeated
every 30 seconds. At this time, the following occurs:

◦ Any data that exists in the master journal on the primary side is sent to the restore journal

on the remote system.

◦ The updated data is then copied to the S-VOL.
◦ Data is updated to the remote system continuously until there is no more data in the master

journal.

◦ Journal data on the primary and secondary systems is discarded when data consistency

is established in the copy.

NOTE: Journal data is transferred using special I/O operations initiated by the secondary

system (RCU), called RIO (remote I/O). RIO provides the most efficient type of data transfer.
Make sure that your channel extenders are capable of supporting RIO. Contact HP Technical
Support for more information.

14 Continuous Access Journal Z overview

If an update copy operation fails, the remote system suspends the affected pair or all Continuous
Access Synchronous Z pairs in the journal. This is dependent on the type of failure. The
suspended pair or journal returns to Paired status when the primary and secondary storage
systems are resynchronized.

Read and Write I/O operations during remote copy operation

The primary system reads from the P-VOL when it receives a read I/O. If the read fails, the
redundancy provided by RAID1 or RAID5 technology recovers the failure. The primary system does
not read the S-VOL for recovery.

When a primary system receives a write I/O for a P-VOL in Duplex status, the system performs the
update copy operation, as well as writing to the P-VOL. The write operation completes independently
of the update copy operations on the S-VOL.

The secondary system updates the S-VOL according to the write sequence number in the journal
data. This maintains data consistency between P-VOL and S-VOL.

If the P-VOL write operation fails, the primary system reports a unit check and does not create the
journal data for this operation. If the update copy operation fails, the secondary system suspends
either the affected pair or all Continuous Access Journal Z pairs in the journal, depending on the
type of failure. When the suspended pair or journal is resumed, the primary and secondary systems
negotiate the resynchronization of the pair(s).

During normal Continuous Access Journal Z operations, the secondary system does not allow
S-VOLs to be online (mounted). Therefore, hosts cannot read from or write to S-VOLs. The S-VOL
write enable option allows write access to a secondary data volume while the pair is split. The
option is only available when you split the pair from the primary system.

When you issue the DEVSERV command to the Continuous Access Journal Z S-VOL, INDETERMINATE
FAILING UNIT is returned if the status of Continuous Access Journal Z S-VOL is online.
INTERVENTION REQUIRED is returned, if the status of Continuous Access Journal Z S-VOL is offline.

S-VOL write option

When a pair is split, you can set an option that will allow write I/O to the S-VOL. The S-VOL write
option is selected during the Suspend Pair operation when performing the operation from the
primary system. When you resynchronize a split pair whose S-VOL is write-enabled, the secondary
system sends the S-VOL track bitmap to the primary system, which merges the P-VOL and S-VOL
bitmaps to determine which tracks are out of sync. This ensures proper resynchronization of the
pair.

S-VOL read option

You can also have a read option enabled for the S-VOL (mode 20) while the pair is suspended.
The secondary system allows you to change the VOLSER of suspended S-VOLs. By setting the mode
20 and the mode 190 to ON, you can change the VOLSER and VTOC of suspended S-VOLs. This
allows the S-VOL to be online to the same host as the P-VOL during the suspend. The primary system
copies the P-VOL VOLSER and VTOC back to the S-VOL when the pair is resynchronized. Make
sure any secondary volumes that were varied online to the host are varied offline before performing
the resync operating. Write I/Os are rejected by the secondary storage system during the suspend.

The primary system copies the P-VOL VOLSER back to the S-VOL when the pair is resumed. When
the S-VOL read option is not enabled and/or the pair is not suspended, the secondary system
rejects read and write I/O to a S-VOL.

Difference management

Differential data (updates during split or suspension) between the P-VOL and S-VOL is stored in a
track bitmap. When a split/suspended pair is resumed, the primary system merges the P-VOL and
S-VOL bitmaps, and the differential data is copied to the S-VOL.

Read and Write I/O operations during remote copy operation 15

The number of bitmap areas affects the maximum possible number of pairs that can be created in
the storage system.

Pair status

Every pair operation results in a change in pair status. You should monitor pair status to insure
that an operation completed successfully. Also, pairs must have a specific status in order for specific
operations to be executed.

The following provides a brief description of the pair statuses. For complete details, see “Pair status

definitions” (page 79) .

• Simplex: A volume that is not assigned to a pair.

• Duplex: When a pair is in the process of being created, the primary system changes the status

of the P-VOL and S-VOL to Pending Duplex.
When the initial copy operation is complete, the primary system changes the status of both

data volumes to Duplex.

• Pending: The initial copy operation for this pair is in progress. This data volume pair is not

yet synchronized.
When the initial copy operation is complete, the primary system changes the status of both

data volumes to Duplex.

• Duplex: This data volume pair is synchronized. Updates to the P-VOL are duplicated on the

S-VOL.
When the initial copy operation is complete, the primary system changes the status of both

data volumes to Duplex.

• Suspended When a pair is split from the primary system, the primary system changes the

status of the P-VOL and S-VOL (if the path status is normal) to Suspended.
When a pair is suspended from the secondary system, it changes the S-VOL status to

Suspended. The primary system detects the pair suspension (if the path status is normal) and
changes P-VOL status to suspended.

• When you release (delete) a pair from the primary system, that system changes the status of

the P-VOL and S-VOL (if the path status is normal) to simplex.
When you release a pair from the secondary system, that system changes S-VOL status to

Simplex. The primary system detects the pair release (if the path status is normal) and changes
P-VOL status to Suspended.

16 Continuous Access Journal Z overview

2 Requirements and specifications

This chapter provides system requirements for Continuous Access Journal Z.

System requirements

Continuous Access Journal Z operations are performed between the host(s) and the primary and
secondary storage systems containing the P-VOLs and S-VOLs, using the data path.

General requirements for the Continuous Access Journal Z components are listed below.

Table 1 General system requirements

RequirementItem

Two—one at the local site, one at the remote site. Also, any combination of the
following can be used with Continuous Access Journal Z:

Number of P9500 systems

• Four on primary side

• Four on secondary side

Continuous Access Journal Z

• Must be installed on primary and secondary P9500 systems.

• License keys required.

• On secondary systems, Continuous Access Journal can coexist with Continuous

Access Journal Z.

Other licenses required

• Continuous Access Synchronous Z is required, whether or not Continuous Access

Journal Z shares volumes with Continuous Access Synchronous Z

• Continuous Access Journal 3DC & 4x4 Open Z MF in the following Continuous

Access Journal Z configurations:

- When running a 3DC system

The track format for the P-VOL and S-VOL must meet the following requirements:Disk Track Format

• The Continuous Access Synchronous Z P-VOL and S-VOL must have the same

track format.

• Record zero (R0) must be standard format, with key length of zero and data

length of eight. The primary system aborts the initial copy operation if R0 is not
standard format.

• The CCHH (logical cylinder address and logical head address) of R0 must be

identical to the physical cylinder address and physical head address of the
track.

• The CCHH of each user record in a track must be unique.

The following program products can be used:

• Remote Web Console

- Required

- Storage Administrator or (Remote Copy) role is required.

Interfaces

• RAID Manager

• Business Continuity Manager

System requirements 17

Table 1 General system requirements (continued)

RequirementItem

Supported mainframe host
platforms

• MVS

• OS/390

• z/OS

• z/VM

• z/Linux

Also, please observe the following:

• Optional error report communications (ERC) function requires MVS/DFP 3.2.0

or later.

• If the primary and/or secondary systems consist of several CPU complexes, a

SYSPLEX timer is required to provide a common time reference for the host I/O
time stamping function. However, the z/Linux operating system does not support
a SYSPLEX timer. As a result, I/O from the z/Linux host is not consistent. Also,
journal consistency is not maintained.

Contact HP Technical Support for the latest information.

Fibre channel.Data path

Volumes

• P-VOL and S-VOL must be equal in size.

• P-VOL and S-VOL must be of same emulation type.

• One Continuous Access Journal Z P-VOL may be copied to one S-VOL only.

• When Continuous Access Synchronous Z is cascaded with Continuous Access

Journal Z, a data volume may be copied to multiple data centers.

Limited per P9500 system. See “Maximum number of pairs allowed ” (page 29).Maximum number of pairs

Continuous Access Journal Z operations between P9500 and previous models are
supported.

Supported previous models

See “Planning for previous models ” (page 35).

RAID1, RAID5, RAID6 can co-exist in the data volumes and journal volumes.Supported RAID groups

Virtual LVI volume is supported.Supported volumes

• Can be used for data and journal volumes.

• S-VOL capacity must equal P-VOL capacity.

Cache Residency volume is supported as follows:

• Data volume: yes

• Journal volume: no

Must be operable for primary and secondary systems to insure pair creation success.
The remote system cache should be configured to adequately support Continuous

Cache and Nonvolatile Storage
(NVS)

Access Journal Z remote-copy workloads, as well as local workload activity. In
general, cache capacity should be increased 25 percent for Continuous Access
Journal Z. Also, an additional GB should be added for each journal on the system.

Required for disaster recovery.Host failover software

Extended consistency groups
(EXCTG)

• A system can have a maximum of four EXCTGs.

• An EXCTG can contain a maximum of 16 registered journals.

18 Requirements and specifications

Table 1 General system requirements (continued)

RequirementItem

RAID Manager consistency groups
when multiple primary and
secondary storage system

• An EXCTG can contain journals from a maximum of four systems.

• A journal cannot be registered in more than one EXCTG.

Journals

• Max. number: 256 (0 to 255) per storage system

• Recommended number: Up to 16

• Max. number of journal volumes: 64 per journal

• Max. number of data volumes: 8,192 per journal

• Journal numbers of master and restore journals that are paired can be different.

• A data volume and associated journal volume can belong to only one journal.

• Data volumes and journal volumes that belong to different controllers cannot

be in the same journal.

• The number of journal volumes in the master journal does not have to be equal

to the number of volumes in the restore journal.

• The P-VOLs and S-VOLs in a journal must be located in one physical primary

system and one physical secondary system (1-to-1 requirement).

• Each pair relationship in a journal is called a "Mirror". Each pair is assigned

a Mirror ID. Max. number of Mirror IDs = 4 (0 to 3).

• When Continuous Access Journal co-exists with Continuous Access Journal Z

in the same storage system, individual journals must be dedicated either to one
or the other, but not both.

• Master and restore journals are managed according to the journal number.

NOTE: The capacity of journal volume is not included in the accounting capacity.

NOTE: Continuous Access Journal can co-exist with Continuous Access Journal Z in the same

storage system.

Business Continuity Manager specifications

Business Continuity Manager commands for Continuous Access Journal Z pair operations are
issued from the host system console to the storage system. With Business Continuity Manager
commands, you can add, suspend, resume, and release pairs, as well as monitor pair status. You
can also add and delete DKC.

The two tables that follow provide values for the P9500 system adapter ID (SAID). For more
information, see the manual of Business Continuity Manager.

Table 2 SAID values for PATH LINK (CL1)

SAIDPortPackage

Local

SAIDPortPackage

Local

SAIDPortPackage

Local

SAIDPortPackage

Local

X'0084'CL9-E1BUX'008C'CL9-N1KUX'0008'CL1-J1GUX'0000'CL1-A1EU

(Add14)(Add10)(Add4)(Basic)

X'00A4'CLB-EX'00AC'CLB-NX'0028'CL3-JX'0020'CL3-A

X'00C4'CLD-EX'00CC'CLD-NX'0048'CL5-JX'0040'CL5-A

X'00E4'CLF-EX'00EC'CLF-NX'0068'CL7-JX'0060'CL7-A

X'0085'CL9-FX'008D'CL9-PX'0009'CL1-KX'0001'CL1-B

X'00A5'CLB-FX'00AD'CLB-PX'0029'CL3-KX'0021'CL3-B

X'00C5'CLD-FX'00CD'CLD-PX'0049'CL5-KX'0041'CL5-B

X'00E5'CLF-FX'00ED'CLF-PX'0069'CL7-KX'0061'CL7-B

Business Continuity Manager specifications 19

Table 2 SAID values for PATH LINK (CL1) (continued)

SAIDPortPackage

Local

SAIDPortPackage

Local

SAIDPortPackage

Local

SAIDPortPackage

Local

X'0086'CL9-G1BLX'008E'CL9-Q1KLX'000A'CL1-L1GLX'0002'CL1-C1EL

(Add12)(Add8)(Add6)(Add2)

X'00A6'CLB-GX'00AE'CLB-QX'002A'CL3-LX'0022'CL3-C

X'00C6'CLD-GX'00CE'CLD-QX'004A'CL5-LX'0042'CL5-C

X'00E6'CLF-GX'00EE'CLF-QX'006A'CL7-LX'0062'CL7-C

X'0087'CL9-HX'008F'CL9-RX'000B'CL1-MX'0003'CL1-D

X'00A7'CLB-HX'00AF'CLB-RX'002B'CL3-MX'0023'CL3-D

X'00C7'CLD-HX'00CF'CLD-RX'004B'CL5-MX'0043'CL5-D

X'00E7'CLF-HX'00EF'CLF-RX'006B'CL7-MX'0063'CL7-D

X'0080'CL9-A1AUX'0088'CL9-J1LUX'000C'CL1-N1HUX'0004'CL1-E1FU

(Add15)(Add5)(Add1)

X'00A0'CLB-AX'00A8'CLB-J(Add11)X'002C'CL3-NX'0024'CL3-E

X'00C0'CLD-AX'00C8'CLD-JX'004C'CL5-NX'0044'CL5-E

X'00E0'CLF-AX'00E8'CLF-JX'006C'CL7-NX'0064'CL7-E

X'0081'CL9-BX'0089'CL9-KX'000D'CL1-PX'0005'CL1-F

X'00A1'CLB-BX'00A9'CLB-KX'002D'CL3-PX'0025'CL3-F

X'00C1'CLD-BX'00C9'CLD-KX'004D'CL5-PX'0045'CL5-F

X'00E1'CLF-BX'00E9'CLF-KX'006D'CL7-PX'0065'CL7-F

X'0082'CL9-C1ALX'008A'CL9-L1LLX'000E'CL1-Q1HLX'0006'CL1-G1FL

(Add13)(Add9)(Add7)(Add3)

X'00A2'CLB-CX'00AA'CLB-LX'002E'CL3-QX'0026'CL3-G

X'00C2'CLD-CX'00CA'CLD-LX'004E'CL5-QX'0046'CL5-G

X'00E2'CLF-CX'00EA'CLF-LX'006E'CL7-QX'0066'CL7-G

X'0083'CL9-DX'008B'CL9-MX'000F'CL1-RX'0007'CL1-H

X'00A3'CLB-DX'00AB'CLB-MX'002F'CL3-RX'0027'CL3-H

X'00C3'CLD-DX'00CB'CLD-MX'004F'CL5-RX'0047'CL5-H

X'00E3'CLF-DX'00EB'CLF-MX'006F'CL7-RX'0067'CL7-H

Table 3 SAID values for PATH LINK (REAR CL2)

SAIDPortPackage

Local

SAIDPortPackage

Local

SAIDPortPackage

Local

SAIDPortPackage

Local

X'0094'CLA-E2NUX'009C'CLA-N2WUX'0018'CL2-J2TUX'0010'CL2-A2QU

(Add14)(Add10)(Add4)(Basic)

X'00B4'CLC-EX'00BC'CLC-NX'0038'CL4-JX'0030'CL4-A

X'00D4'CLE-EX'00DC'CLE-NX'0058'CL6-JX'0050'CL6-A

X'00F4'CLG-EX'00FC'CLG-NX'0078'CL8-JX'0070'CL8-A

X'0095'CLA-FX'009D'CLA-PX'0019'CL2-KX'0011'CL2-B

X'00B5'CLC-FX'00BD'CLC-PX'0039'CL4-KX'0031'CL4-B

X'00D5'CLE-FX'00DD'CLE-PX'0059'CL6-KX'0051'CL6-B

X'00F5'CLG-FX'00FD'CLG-PX'0079'CL8-KX'0071'CL8-B

20 Requirements and specifications

Table 3 SAID values for PATH LINK (REAR CL2) (continued)

SAIDPortPackage

Local

SAIDPortPackage

Local

SAIDPortPackage

Local

SAIDPortPackage

Local

X'0096'CLA-G2NLX'009E'CLA-Q2WLX'001A'CL2-L2TLX'0012'CL2-C2QL

(Add12)(Add8)(Add6)(Add2)

X'00B6'CLC-GX'00BE'CLC-QX'003A'CL4-LX'0032'CL4-C

X'00D6'CLE-GX'00DE'CLE-QX'005A'CL6-LX'0052'CL6-C

X'00F6'CLG-GX'00FE'CLG-QX'007A'CL8-LX'0072'CL8-C

X'0097'CLA-HX'009F'CLA-RX'001B'CL2-MX'0013'CL2-D

X'00B7'CLC-HX'00BF'CLC-RX'003B'CL4-MX'0033'CL4-D

X'00D7'CLE-HX'00DF'CLE-RX'005B'CL6-MX'0053'CL6-D

X'00F7'CLG-HX'00FF'CLG-RX'007B'CL8-MX'0073'CL8-D

X'0090'CLA-A2MUX'0098'CLA-J2XUX'001C'CL2-N2UUX'0014'CL2-E2RU

(Add15)(Add11)(Add5)(Add1)

X'00B0'CLC-AX'00B8'CLC-JX'003C'CL4-NX'0034'CL4-E

X'00D0'CLE-AX'00D8'CLE-JX'005C'CL6-NX'0054'CL6-E

X'00F0'CLG-AX'00F8'CLG-JX'007C'CL8-NX'0074'CL8-E

X'0091'CLA-BX'0099'CLA-KX'001D'CL2-PX'0015'CL2-F

X'00B1'CLC-BX'00B9'CLC-KX'003D'CL4-PX'0035'CL4-F

X'00D1'CLE-BX'00D9'CLE-KX'005D'CL6-PX'0055'CL6-F

X'00F1'CLG-BX'00F9'CLG-KX'007D'CL8-PX'0075'CL8-F

X'0092'CLA-C2MLX'009A'CLA-L2XLX'001E'CL2-Q2ULX'0016'CL2-G2RL

(Add13)(Add9)(Add7)(Add3)

X'00B2'CLC-CX'00BA'CLC-LX'003E'CL4-QX'0036'CL4-G

X'00D2'CLE-CX'00DA'CLE-LX'005E'CL6-QX'0056'CL6-G

X'00F2'CLG-CX'00FA'CLG-LX'007E'CL8-QX'0076'CL8-G

X'0093'CLA-DX'009B'CLA-MX'001F'CL2-RX'0017'CL2-H

X'00B3'CLC-DX'00BB'CLC-MX'003F'CL4-RX'0037'CL4-H

X'00D3'CLE-DX'00DB'CLE-MX'005F'CL6-RX'0057'CL6-H

X'00F3'CLG-DX'00FB'CLG-MX'007F'CL8-RX'0077'CL8-H

Command device

To use Business Continuity Manager, you can configure a command device for it separately from
the command device for an open system. The command device for Business Continuity Manager
can be configured only from Business Continuity Manager. For details, see the manual of Business
Continuity Manager.

Command device 21

3 Planning volumes, systems

This chapter provides information and instructions for planning Continuous Access Journal Z volumes,
P9500 systems, and other important requirements and restrictions.

Plan and design workflow

Planning the Continuous Access Journal Z system is tied to your organization’s business requirements
and production system workload. This means defining business requirements for disaster downtime
and measuring the amount of changed data your system produces over time. With this information,
you can calculate the size that journal volumes must be and the amount of bandwidth required to
transfer update data over the data path network.

The plan and design workflow consists of the following:

• Assess your organization’s business requirements to determine recovery requirements.

• Measure your host application’s write-workload in MB per second and write-input/output per

second (IOPS) to begin matching actual data loads with the future Continuous Access Journal
Z system.

• Use collected data along with your organization’s recovery point objective (RPO) to size

Continuous Access Journal Z journal volumes. Journal volumes must have enough capacity to
hold accumulating data over extended periods.

The size of the journal volumes is dependent on the amount of bandwidth needed. You adjust
journal volume size in conjunction with bandwidth to fit the organization’s needs.

• Use IOPS to determine data transfer speed into and out of the journal volumes. Data transfer

speed is determined by the number of Fibre Channel ports you assign to Continuous Access
Journal Z, and by RAID group configuration. You need to know port transfer capacity and
the number of ports that your workload data will require.

• Use the collected workload data to determine the bandwidth for the Fibre Channel data path.

As mentioned, bandwidth and journal volume sizing, along with data transfer speed, are
interrelated. Bandwidth may be adjusted in conjunction with the journal volume capacity and
data transfer speed you plan to implement.

• Design the data path network configuration. This involves: understanding supported

configurations, the need for Fibre Channel switches, and the number of ports your data transfer
requires.

• Plan data volumes (primary and secondary volumes). This involves understanding the sizing

of P-VOL and S-VOL, and RAID group considerations.

• Understand operating system requirements for data and journal volumes.

• Adjust cache memory capacity for Continuous Access Journal Z.

Some tasks will be handled by HP personnel. The planning information you need to address is
provided in the following sections.

Assessing business requirements for data recovery

In a Continuous Access Journal Z system, when the data path continues to transfer changed data
to the remote site, journals remain fairly empty. However, if a path failure or a prolonged spike
in write-data that is greater than bandwidth occurs, data is stored in the journal. Changed data
that is no longer moving to the remote system builds up in the master journal.

22 Planning volumes, systems

To insure that journals can hold the amount of data that could accumulate, they must be sized
according to the following:

• The maximum amount of time that journals could accumulate data. You develop this information

by determining your operation’s recovery point objective (RPO).

• The amount of changed data that your application generates. This is done by measuring

write-workload.

Determining your RPO

Your operation’s recovery point is the maximum time that can pass after a failure or disaster occurs
before data loss is greater than the operation can survive.

For example, if the operation can survive one hour’s worth of lost data, and a disaster occurs at
10:00 a.m., then the system must be corrected by 11:00 a.m.

In regards to journal sizing, the journal must have the capacity to hold the data that could
accumulated in one hour. If RPO is 4 hours, then the journal must be sized to hold 4 hours' worth
of accumulating data.

To assess RPO, the host application’s write-workload must be known.
With write-workload and IOPS, you or your organization’s system administrator can analyze the

number of transactions write-workload represents, determine the number of transactions the operation
could loose and still remain viable, determine the amount of time required to recover lost data from
log files or key it in, and so on. The result is your RPO.

Write-workload

Write-workload is the amount of data that changes in your production system in MB per second.
As you will see, write-workload varies. according to the time of day, week, month, quarter. That
is why workload is measured over an extended period.

With the measurement data, you can calculate workload averages, locate peak workload, and
calculate peak rolling averages, which show an elevated average. With one of these base data
you will calculate the amount of data that accumulates over your RPO time, for example, 2 hours.
This will be a base capacity for your journal volumes or represent a base amount of bandwidth
your system requires.

Whether you select average, rolling average, or peak workload is based on the amount of
bandwidth you will provide the data path (which is also determined by write-workload). Bandwidth
and journal volume capacity work together and depend on your strategy for protecting data.

Measuring write-workload

Workload data is collected using Performance Monitor or your operating system’s
performance-monitoring feature. The number of read/write transactions, or input/output per second
(IOPS), is also collected by the software. You will use IOPS to set up a proper data transfer speed,
which you insure through RAID group configuration and by establishing the number of Fibre Channel
ports your Continuous Access Journal Z system requires. Each RAID group has a maximum
transaction throughput; the ports and their microprocessors have an IOPS threshold.

Workload and IOPS collection is best performed during the busiest time of month, quarter, and
year. This helps you to collect data that shows your system’s actual workloads during high peaks
and spikes, when more data is changing, and when the demands on the system are greatest.
Collecting data over these periods insures that the Continuous Access Journal Z design you develop
will support your system in all workload levels.

Write-workload 23

To measure write-workload and IOPS

1. Using your performance monitoring software, collect the following:

• Disk-write bytes-per-second (MB/s) for every physical volume that will be replicated.

• Data should be collected over a 3 or 4 week period to cover a normal, full business cycle.

• Data should be collected at 5 minute intervals. If you use averages, shorter intervals

provide more accuracy.

2. At the end of the collection period, convert the data to MB, if needed, and import into a
spreadsheet tool.

Sizing journal volumes

Determine the required journal volume capacity

The following factors determine the required journal volume capacity:

• The period of time during which data transfer can continue between hosts and the primary

storage system when a temporary increase in transferred data occurs or when a communication
path failure occurs between the primary and secondary storage system.

• The data transfer speed for the period of time mentioned above.

To determine the journal volume capacity, use the following formula:
Formula 1 : Journal volume capacity > (V

H-M

- V

M-R

) × t

where:

• V

H-M

is the data transfer speed between hosts and the primary storage system.

• V

M-R

is the data transfer speed between the primary storage system and the secondary storage

system.

• t is the length of time during which data transfer can continue.

To calculate journal volume capacity that is required when a communication path failure occurs
between the primary storage system and the secondary storage system, assign zero (0) to V

M-R

.

The total capacity of journal volumes in each journal group must exceed the value illustrated in
formula 1.

When the data in the primary data volume of the Continuous Access Journal Z delta resync pair
is updated, if the journal data that exceeds 70 percent of the journal volume capacity on the
primary site of the Continuous Access Journal Z delta resync pair is generated, the delta resync
operation will fail. Therefore, adopt the larger value for the journal volume capacity on the primary
site of the Continuous Access Journal Z delta resync pair by comparing the values of formula 1
and formula 2.

Formula 2 : Journal volume capacity > (V × t) × 1.5

24 Planning volumes, systems

where:

• V is the data transfer speed between a host and the primary storage system.

• t is the length of time until the delta resync operation starts.

CAUTION: The journal volume capacity is recommended to be over 6 GB. If the capacity is

below 6 GB, the system performance is unassured because the following problems may occur.

• The new data cannot be stored because the journal volume is full and host performance is

reduced.

• The performance of the initial copy goes down because the journal volume is full.

• The journal group is suspended because the journal volume is full.

• The Usage Monitor value is invalid.

Calculating the journal size

You calculate the size your journal volumes using the write-workload and RPO.

To calculate journal size

1. Follow the instructions for “Measuring write-workload” (page 23).

2. Use your system’s peak write-workload and your organization’s RPO to calculate journal size.
For example:

RPO = 2 hours

Write-workload = 30 MB/sec

Calculate write-workload for the RPO. In the example, write-workload over a 2 hours period
is calculated as follows:

30 MB/second x 60 seconds = 1800 MB/minute

1800 MB/minute x 60 minutes = 108,000 MB/hour

108000 MB/hour x 2 = 416,000 MB/2 hours

Basic journal volume size = 416,000 MB (416 GB)

Journal volume capacity and bandwidth size work together. Also, your strategy for protecting your
data may allow you to adjust bandwidth or the size of your journal volumes. For a discussion on
sizing strategies, see “Five sizing strategies ” (page 39).

NOTE: If you are planning for disaster recovery, the remote array must be large enough to handle

the production workload, and therefore, must be the same size as master journals. If not planning
a disaster recovery solution, remote journal volumes may be smaller than master journal volumes.

Planning journals

Continuous Access Journal Z manages pair operations for data consistency through the use of
journals. Continuous Access Journal Z journals enable update sequence consistency to be maintained
across a group of volumes.

Understanding the consistency requirements for an application (or group of applications) and their
volumes will indicate how to structure journals.

For example, databases are typically implemented in two sections. The bulk of the data is resident
in a central data store, while incoming transactions are written to logs that are subsequently applied
to the data store.

If the log volume “gets ahead” of the data store, it is possible that transactions could be lost at
recovery time. Therefore, to insure a valid recovery image on a replication volume, it is important
that both the data store and logs are I/O consistent by placing them in the same journal.

Sizing journal volumes 25

To plan journals, see the following:

• Review journal specifications in “System requirements” (page 17).

• Review journal configuration in “Register journal volumes in a journal” (page 62).

Data transfer speed considerations

The previous sections and the sections later in this chapter on Bandwidth discuss the amount of
data that must be stored temporarily in journals and transferred over the data path network. This
section discusses the speed that data must be transferred in order to maintain the Continuous Access
Journal Z system your are designing.

The ability of your Continuous Access Journal Z system to transfer data in a timely manner depends
directly on the following two factors:

• RAID group configuration

• Fibre Channel port configuration

Both of these elements must be planned to be able to handle the amount of data and number of
transactions your system will process under extreme conditions.

RAID group configuration

A RAID group can consist of physical volumes with a different number of revolutions, physical
volumes of different capacities, and physical volumes of different RAID configurations (for example,
RAID1 and RAID5). The data transfer speed of RAID groups is affected by physical volumes and
RAID configurations.

• The data transfer speed of a journal volume depends on the data transfer speed of the RAID

group to which it belongs. A RAID group can consist of one or more volumes, including journal
volumes.

• Journal volumes must be configured in RAID groups according to the group’s throughput

specification and your system’s peak write-workload. If write-workload exceeds the RAID
group’s throughput rating, then the number of RAID groups must be increased.

• Frequent read/write activity to non-journal volumes in a RAID group results in fewer read/writes

by journal volumes in the same RAID group. This can cause a drop in the data transfer speed
of journal volumes. To avoid this effect, place journal volumes and frequently accessed
non-journal volumes in different RAID groups.

Fibre Channel port configuration

The Fibre Channel ports on your P9500 system have an IOPS threshold. Use the performance
monitoring information for the number of IOPS your production system generates to calculate the
number of Fibre Channel ports the Continuous Access Journal Z system requires.

See “Planning ports for data transfer ” (page 43) for a full discussion on the type and number of
Fibre Channel ports required for your system.

Planning journal volumes

The following information is provided to help you prepare journal volumes:

• Identify the journal volumes for your Continuous Access Journal Z system on primary and

secondary arrays. Journal volumes should be sized according to RPO and write-workload.
See “Sizing journal volumes” (page 24) for more information.

• Journal volumes in the same journal can be of different capacity. A master journal volume

and the corresponding restore journal volume can be of different capacity.

• Journal volumes consist of two areas: one area is used for storing journal data, and the other

area is used for storing metadata.

26 Planning volumes, systems

• Journal volumes support all RAID configurations that are supported by P9500. Journal volumes

also support all physical volumes that are supported by P9500.

• Customized volumes can be used for journal volumes.

See “Calculating maximum number of pairs” (page 29) for maximum and minimum supported
capacity of journal volumes.

See system requirements and specifications in “Requirements and specifications” (page 17) for
more information.

Host I/O time stamp

The I/O time stamping function must be installed on the host processor at the primary site in order
to provide data consistency in Continuous Access Journal Z journals. The I/O time stamp, which
is provided by MVS DFSMSdfp, is the same time stamp that is used by Compatible XRC pairs. The
I/O time stamping function should also be installed on the host processor at the secondary site,
so that time stamps can be used when copying data in the reverse direction.

If the system at the primary and/or secondary site consists of several CPU complexes, a SYSPLEX
timer is required to provide a common time reference for the I/O time stamping function.

Planning pair volumes

The following information is provided to help you prepare volumes for configuration. Also, see
system requirements and specifications in “Requirements and specifications” (page 17) for more
information.

• The emulation and capacity for the S-VOL must be the same as the P-VOL.

• When the S-VOL is connected to the same host as the P-VOL, the S-VOL must be defined to

remain offline.

• The following CU emulation types can be used for MCUs (primary systems) and RCUs

(secondary systems): 2105, 2107.

• The CU emulation type 2105, or 2107 is required for SMS I/O time stamping of Continuous

Access Journal Z journals. When one of these CU emulation types is used, volumes of most
3380 emulation types must not be used. Only 3380-3 can be used.

• Continuous Access Journal Z supports the Virtual LVI feature, which allows you to configure

custom-size LDEVs that are smaller than standard-size LDEVs. When custom-size LDEVs are
assigned to a Continuous Access Journal Z pair, the S-VOL must have the same capacity as
the P-VOL. For details about Virtual LVI feature, see HP StorageWorks P9000 Provisioning for
Mainframe Systems User Guide.

• Identify the volumes that will become the P-VOLs and S-VOLs.

• You can create multiple pairs at the same time. For details, see (page 66).

• When you create a Continuous Access Journal Z pair, you will have the option to create only

the relationship, without copying data from primary to secondary volumes. You can use this
option only when the contents of the primary and secondary data volume are completely the
same.

Data and journal volume specifications

The following table shows maximum capacities and volume types that can be used for data volumes
and journal volumes.

Planning pair volumes 27

Table 4 Data and journal volume specifications

Support specificationsType

Journal volumeData volume

AvailableAvailableVirtual LVI volume

UnavailableAvailableCache Residency Z volume

2.377 GB2.377 GB3380-3Maximum volume

capacity

1.26 GB1.26 GB3380-E

0.63 GB0.63 GB3380-J

1.890 GB1.890 GB3380-K

0.964GB0.964GB3390-1

1.892GB1.892GB3390-2

2.838GB2.838GB3390-3

3390-3R

8.510GB8.510GB3390-9

27.80GB27.80GB3390-L

55.60GB55.60GB3390-M

Capacity of OPEN-V volumes can be
determined freely, and has dependencies on

Cannot be used as data
volumes.

OPEN-V

Virtual LVI volume specifications. The minimum
capacity is 48.1 MB, and the maximum
capacity is the same as the user capacity of
one RAID group.

The default capacity of an OPEN-V volume is
the same as the capacity of a RAID group, and
depends on the hard disk drive type and the
RAID configuration.

50 cylinders for a non-OPEN-V volume.1 cylinderMinimum volume capacity

48.1 MB for an OPEN-V volume.

Duplicating VOLSERs

When the P-VOL is copied to the S-VOL during the initial copy operation, the P-VOL VOLSER
(Volume Serial Number) is also copied to the S-VOL. Therefore, the P-VOL and S-VOL have the
same VOLSER. Because the host operating system does not allow duplicate VOLSERs, the host
system administrator must take precautions to prevent system problems related to duplicate VOLSERs
(such as defining Continuous Access Journal Z S-VOLs not to come online automatically).

CAUTION: If the volumes that become Continuous Access Journal Z S-VOLs are physically attached

to the same system images as the volumes that become the Continuous Access Journal Z P-VOLs,
the potential for error increases. For example, when a Continuous Access Journal Z pair is released,
the old S-VOL is usually offline. When a host system is IPL’d (initial program loaded), the operator
is offered both volumes and asked which volume should be left offline. You can avoid duplication
of the VOLSER as follows:

1. Identify the volumes that are not accessed by the host system.

2. Perform CHP OFF or some other operation to insure that the volumes are inaccessible.

3. When performing IPL, make sure to perform LOAD CLEAR.

28 Planning volumes, systems

Maximum number of pairs allowed

P9500 has a limit on the number of pairs that can be created. Therefore, it is necessary to calculate
the maximum number of pairs on the P9500 storage system. The maximum number is limited
according to the following:

1. The number of cylinders in the volumes, which must be calculated.

2. The number of bitmap areas required for Continuous Access Journal data and journal volumes.
This is calculated using the number of cylinders.

3. The maximum number of pairs that can be created, calculated using the number of required
bitmap areas.

CAUTION: The bitmap areas that are used for Continuous Access Journal are also used for

Continuous Access Journal Z, Continuous Access Synchronous, Continuous Access Synchronous
Z, and External Storage Access Manager. If you use Continuous Access Journal with Continuous
Access Journal Z, Continuous Access Synchronous, and Continuous Access Synchronous Z, use
the total number of each pair’s bitmap areas to calculate the maximum number of pairs. In addition,
if Continuous Access Journal and Continuous Access Synchronous share the same volume, use the
total number of both pairs regardless of whether the shared volume is primary or secondary.

Calculating maximum number of pairs

NOTE: In the calculations below, ceil() indicate that the value between the parentheses should

be rounded up to the nearest integer.

To determine the number of cylinders

The number of cylinders according to the emulation type are listed below.

Table 5 Number of cylinders per emulation type

Number of cylindersEmulation type

3,3393380-3

3,3393390-3, 3390-3R

10,0173390-9

32,7603390-L

65,5203390-M

To calculate the number of required bitmap areas:

Use the following formula

Required number of bitmap areas = (ceil((number of cylinders x 15)
122,752) )

where:
“number of cylinders x 15” indicates the number of slots
122,752 = the number of slots that a bitmap area can manage

To calculate the maximum number of pairs that can be created

The maximum number of pairs you can create is defined by the following:

• The number of LDEVs in the storage system

Planning pair volumes 29

Table 6 The relationship between installed additional shared memory and the total number of
LDEVs in the storage system

Total number of LDEVs in storage systemInstalled additional shared memory for Cnt Ac-J Z

16,384Base(16KLDEV,BC/VM)

65,28064KLDEV,BC/VM Extension1,FCV2,DP,Snapshot,TPF

• The number of bitmap areas required to create pairs (determined above)

• The number of bitmap areas of the storage system is 65,536.

Use the following formulae to calculate the maximum possible number of pairs that can be created,
on the basis of the number of bitmap areas and the required number of bitmap areas you calculated:

Maximum number of pairs = floor( Number of bitmap areas required number
of bitmap areas )

The maximum number of pairs is limited to 32,768.
If the calculated maximum number of pairs exceeds the total number of LDEVs of the storage system,

the total number of LDEVs in the storage system is the maximum number of pairs that can be created.

Priority set for initial copy operations and scheduling order

For performing more initial copy operations than the setting value of the Maximum Initial Copy
Activities set on the System Option dialog box, the scheduling order (Priority) can be set for the
initial copy operations to be performed. This section explains the assignment of the scheduling
order of initial copy operations in cases where two sets of multiple initial copy operations are
performed.

An example is described in which 4 data volume pairs are created at the same time in cases where
the setting value of the Maximum Initial Copy Activities is 2. The Priority which is set for the P-VOLs
of data volume pairs is shown in the following table.

Table 7 Priority set for P-VOLs for which initial copy operation is performed

Value set for PriorityP-VOL

2LDEV 00

3LDEV 01

1LDEV 02

4LDEV 03

The order of starting initial copy and the Priority which is set for the P-VOLs are shown in the
following table.

Table 8 Correspondence relationship between order of starting initial copy and priority set for
P-VOLs

Value set for PriorityP-VOLOrder of starting initial copy

1LDEV 021

2LDEV 002

3LDEV 013

4LDEV 034

In this case, as the setting value of the Maximum Initial Copy Activities is 2, initial copy operations
for LDEV 02 and LDEV 00 are started. If either one of the initial copy operations for LDEV 02 and
LDEV 00 is completed, the initial copy for LDEV 01 is started.

30 Planning volumes, systems