Intel AS-400 RISC, 7xx, 170 User Manual

IBM Power Systems

Performance Capabilities Reference

IBM i operating system Version 6.1

January/April/October 2008

This document is intended for use by qualified performance related programmers or analysts from IBM, IBM Business Partners and IBM customers using the IBM Power running IBM i operating system. Information in this document may be readily shared with IBM i customers to understand the performance and tuning factors in IBM i operating system

6.1 and earlier where applicable. For the latest updates and for the latest on IBM i

performance information, please refer to the Performance Management Website:

http://www.ibm.com/systems/i/advantages/perfmgmt/index.html

Requests for use of performance information by the technical trade press or consultants should be directed to Systems Performance Department V3T, IBM Rochester Lab, in Rochester, MN. 55901 USA.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

Systems platform

Note!

Before using this information, be sure to read the general information under “Special Notices.”

Twenty Fifth Edition (January/April/October 2008) SC41-0607-13

This edition applies to IBM i operating System V6.1 running on IBM Power Systems.

You can request a copy of this document by download from IBM i Center via the System i Internet site at:

http://www.ibm.com/systems/i/

available on the IBM iSeries Internet site in the "On Line Library", at: http://publib.boulder.ibm.com/pubs/html/as400/online/chgfrm.htm.

Documents are viewable/downloadable in Adobe Acrobat (.pdf) format. Approximately 1 to 2 MB download. Adobe Acrobat reader plug-in is available at: http://www.adobe.com

To request the CISC version (V3R2 and earlier), enter the following command on VM:

REQUEST V3R2 FROM FIELDSIT AT RCHVMW2 (your name)

To request the IBM iSeries Advanced 36 version, enter the following command on VM:

TOOLCAT MKTTOOLS GET AS4ADV36 PACKAGE

Note to U.S. Government Users -- Documentation related to restricted rights -- Use, duplication, or disclosure is subject to restrictions set forth in GSA ADP Schedule Contract with IBM Corp.

. The Version 5 Release 1 and Version 4 Release 5 Performance Capabilities Guides are also

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

2.1 Overview

2.1.1 Interactive Indicators and Metrics

2.1.2 Disclaimer and Remaining Sections

2.1.3 V5R3

2.1.4 V5R2 and V5R1

2.2 Server Model Behavior

2.2.1 In V4R5 - V5R2

2.2.2 Choosing Between Similarly Rated Systems

2.2.3 Existing Older Models

2.3 Server Model Differences

2.4 Performance Highlights of Model 7xx Servers

2.5 Performance Highlights of Model 170 Servers

2.6 Performance Highlights of Custom Server Models

2.7 Additional Server Considerations

2.8 Interactive Utilization

2.9 Server Dynamic Tuning (SDT)

2.10 Managing Interactive Capacity

2.11 Migration from Traditional Models

2.12 Upgrade Considerations for Interactive Capacity

2.13 iSeries for Domino and Dedicated Server for Domino Performance Behavior

2.13.1 V5R2 iSeries for Domino & DSD Performance Behavior updates

2.13.2 V5R1 DSD Performance Behavior

3.1 Effect of CPU Speed on Batch

3.2 Effect of DASD Type on Batch

3.3 Tuning Parameters for Batch

4.1 New for i5/OS V6R1

i5/OS V6R1 SQE Query Coverage

4.2 DB2 i5/OS V5R4 Highlights

i5/OS V5R4 SQE Query Coverage

4.3 i5/OS V5R3 Highlights

i5/OS V5R3 SQE Query Coverage Partitioned Table Support

4.4 V5R2 Highlights - Introduction of the SQL Query Engine

4.5 Indexing

4.6 DB2 Symmetric Multiprocessing feature

4.7 DB2 for i5/OS Memory Sharing Considerations

4.8 Journaling and Commitment Control

4.9 DB2 Multisystem for i5/OS

4.10 Referential Integrity

4.11 Triggers

4.12 Variable Length Fields

4.13 Reuse Deleted Record Space

4.14 Performance References for DB2

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10Special Notices ....................................................................

12Purpose of this Document ...........................................................

13Chapter 1. Introduction ............................................................

14Chapter 2. iSeries and AS/400 RISC Server Model Performance Behavior .................

14 14 15 15 16 16 16 17 17 19 21 22 23 23 24 25 28 31 33 34 34 34

38Chapter 3. Batch Performance ......................................................

38 38 39

41Chapter 4. DB2 for i5/OS Performance ...............................................

41 41 44 44 45 45 47 49 51 52 53 53 56 57 58 59 61 62

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

5.2 Communication Performance Test Environment

5.5 TCP/IP Secure Performance

5.6 Performance Observations and Tips

5.7 APPC, ICF, CPI-C, and Anynet

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5.8 HPR and Enterprise extender considerations

5.9 Additional Information

6.1 HTTP Server (powered by Apache)

6.2 PHP - Zend Core for i

6.3 WebSphere Application Server

6.4 IBM WebFacing

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6.5 WebSphere Host Access Transformation Services (HATS)

6.6 System Application Server Instance

6.7 WebSphere Portal

6.8 WebSphere Commerce

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6.9 WebSphere Commerce Payments

6.10 Connect for iSeries

7.1 Introduction

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7.2 What’s new in V6R1

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7.3 IBM Technology for Java (32-bit and 64-bit)

Native Code Garbage Collection

7.4 Classic VM (64-bit)

JIT Compiler Garbage Collection Bytecode Verification

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7.5 Determining Which JVM to Use

7.6 Capacity Planning

General Guidelines

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7.7 Java Performance – Tips and Techniques

Introduction

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i5/OS Specific Java Tips and Techniques Classic VM-specific Tips

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Java Language Performance Tips Java i5/OS Database Access Tips

Resources

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8.1 System i Cryptographic Solutions

8.2 Cryptography Performance Test Environment

8.3 Software Cryptographic API Performance

8.4 Hardware Cryptographic API Performance

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8.5 Cryptography Observations, Tips and Recommendations

8.6 Additional Information

9.1 iSeries NetServer File Serving Performance

10.1 DB2 for i5/OS access with JDBC

JDBC Performance Tuning Tips References for JDBC

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63Chapter 5. Communications Performance .............................................

65 68 71 73 75 77

78Chapter 6. Web Server and WebSphere Performance ..................................

79 88

93 107 117 119 121 121 122 122

126Chapter 7. Java Performance ......................................................

126 126 127 128 128 129 129 131 132 133 135 135 136 136 137 137 138 141 142

143Chapter 8. Cryptography Performance ..............................................

143 144 145 146 148 149

150Chapter 9. iSeries NetServer File Serving Performance ................................

150

153Chapter 10. DB2 for i5/OS JDBC and ODBC Performance .............................

153 153 154

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

10.2 DB2 for i5/OS access with ODBC

References for ODBC

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11.1 Domino Workload Descriptions

11.2 Domino 8

11.3 Domino 7

11.4 Domino 6

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Notes client improvements with Domino 6 Domino Web Access client improvements with Domino 6

11.5 Response Time and Megahertz relationship

11.6 Collaboration Edition and Domino Edition offerings

11.7 Performance Tips / Techniques

11.8 Domino Web Access

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11.9 Domino Subsystem Tuning

11.10 Performance Monitoring Statistics

11.11 Main Storage Options

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11.12 Sizing Domino on System i

11.13 LPAR and Partial Processor Considerations

11.14 System i NotesBench Audits and Benchmarks

12.1 Introduction

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12.2 Performance Improvements for WebSphere MQ V5.3 CSD6

12.3 Test Description and Results

12.4 Conclusions, Recommendations and Tips

13.1 Summary

Key Ideas

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13.2 Basic Requirements -- Where Linux Runs

13.3 Linux on iSeries Technical Overview

Linux on iSeries Architecture Linux on iSeries Run-time Support

13.4 Basic Configuration and Performance Questions

13.5 General Performance Information and Results

Computational Performance -- C-based code Computational Performance -- Java Web Serving Performance Network Operations

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Gcc and High Optimization (gcc compiler option -O3) The Gcc Compiler, Version 3

13.6 Value of Virtual LAN and Virtual Disk

Virtual LAN Virtual Disk

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13.7 DB2 UDB for Linux on iSeries

13.8 Linux on iSeries and IBM eServer Workload Estimator

13.9 Top Tips for Linux on iSeries Performance

14.1 Internal (Native) Attachment.

14.1.0 Direct Attach (Native)

14.1.1 Hardware Characteristics

14.1.2 iV5R2 Direct Attach DASD

14.1.3 571B

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155 157

158Chapter 11. Domino on i ..........................................................

159 160 160 161 161 162 163 164 164 167 168 168 169 172 173 174

175Chapter 12. WebSphere MQ for iSeries .............................................

175 175 176 176

178Chapter 13. Linux on iSeries Performance ...........................................

178 178 178 179 179 180 181 182 182 183 183 184 184 185 185 185 185 186 187 187

191Chapter 14. DASD Performance ...................................................

191 192 192 193 195

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

14.1.3.1 571B RAID5 vs RAID6 - 10 15K 35GB DASD

14.1.3.2 571B IOP vs IOPLESS - 10 15K 35GB DASD

14.1.4 571B, 5709, 573D, 5703, 2780 IOA Comparison Chart

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14.1.5 Comparing Current 2780/574F with the new 571E/574F and 571F/575B NOTE: iV5R3 has support for the features in this section but all of our performance measurements were done on iV5R4 systems. For information on the

supported features see the IBM Product Announcement Letters. ..........................

14.1.6 Comparing 571E/574F and 571F/575B IOP and IOPLess

14.1.7 Comparing 571E/574F and 571F/575B RAID5 and RAID6 and Mirroring

14.1.8 Performance Limits on the 571F/575B

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14.1.9 Investigating 571E/574F and 571F/575B IOA, Bus and HSL limitations.

14.1.10 Direct Attach 571E/574F and 571F/575B Observations

14.2 New in iV5R4M5

14.2.1 9406-MMA CEC vs 9406-570 CEC DASD

14.2.2 RAID Hot Spare

14.2.3 12X Loop Testing

14.3 New in iV6R1M0

14.3.1 Encrypted ASP

14.3.2 57B8/57B7 IOA

14.3.3 572A IOA

14.4 SAN - Storage Area Network (External)

14.5.1 General VIOS Considerations

14.5.1.1 Generic Concepts

14.5.1.2 Generic Configuration Concepts

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14.5.1.3 Specific VIOS Configuration Recommendations -- Traditional (non-blade)

Machines ........................................................................

14.5.1.3 VIOS and JS12 Express and JS22 Express Considerations

14.5.1.3.1 BladeCenter H JS22 Express running IBM i operating system/VIOS

14.5.1.3.2 BladeCenter S and JS12 Express

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14.5.1.3.3 JS12 Express and JS22 Express Configuration Considerations

14.5.1.3.4 DS3000/DS4000 Storage Subsystem Performance Tips

14.6 IBM i operating system 5.4 Virtual SCSI Performance

14.6.1 Introduction

14.6.2 Virtual SCSI Performance Examples

14.6.2.1 Native vs. Virtual Performance

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14.6.2.2 Virtual SCSI Bandwidth-Multiple Network Storage Spaces

14.6.2.3 Virtual SCSI Bandwidth-Network Storage Description (NWSD) Scaling

14.6.2.4 Virtual SCSI Bandwidth-Disk Scaling

14.6.3 Sizing

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14.6.3.1 Sizing when using Dedicated Processors

14.6.3.2 Sizing when using Micro-Partitioning

14.6.3.3 Sizing memory

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14.6.4 AIX Virtual IO Client Performance Guide

14.6.5 Performance Observations and Tips

14.6.6 Summary

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15.1 Supported Backup Device Rates

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15.2 Save Command Parameters that Affect Performance

Use Optimum Block Size (USEOPTBLK) Data Compression (DTACPR) Data Compaction (COMPACT)

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195 195 196

198 199 200 202 203 205 206 206 207 208 209 209 211 213 214 216 216 217

220 222 222 227 228 229 231 233 234 235 235 236 237 238 238 240 241 242 242 242

243Chapter 15. Save/Restore Performance ..............................................

243 244 244 244 244

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

15.3 Workloads

15.4 Comparing Performance Data

15.5 Lower Performing Backup Devices

15.6 Medium & High Performing Backup Devices

15.7 Ultra High Performing Backup Devices

15.8 The Use of Multiple Backup Devices

15.9 Parallel and Concurrent Library Measurements

15.9.1 Hardware (2757 IOAs, 2844 IOPs, 15K RPM DASD)

15.9.2 Large File Concurrent

15.9.3 Large File Parallel

15.9.4 User Mix Concurrent

15.10 Number of Processors Affect Performance

15.11 DASD and Backup Devices Sharing a Tower

15.12 Virtual Tape

15.13 Parallel Virtual Tapes

15.14 Concurrent Virtual Tapes

15.15 Save and Restore Scaling using a Virtual Tape Drive.

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15.16 Save and Restore Scaling using 571E IOAs and U320 15K DASD units to a

3580 Ultrium 3 Tape Drive. .........................................................

15.17 High-End Tape Placement on System i

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15.18 BRMS-Based Save/Restore Software Encryption and DASD-Based ASP

Encryption ......................................................................

15.19 5XX Tape Device Rates

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15.20 5XX Tape Device Rates with 571E & 571F Storage IOAs and 4327 (U320)

Disk Units .......................................................................

15.21 5XX DVD RAM and Optical Library

15.23 9406-MMA DVD RAM

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15.24 9406-MMA 576B IOPLess IOA

16.1 IPL Performance Considerations

16.2 IPL Test Description

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16.3 9406-MMA System Hardware Information

16.3.1 Small system Hardware Configuration

16.3.2 Large system Hardware Configurations

16.4 9406-MMA IPL Performance Measurements (Normal)

16.5 9406-MMA IPL Performance Measurements (Abnormal)

16.6 NOTES on MSD

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16.6.1 MSD Affects on IPL Performance Measurements

16.7 5XX System Hardware Information

16.7.1 5XX Small system Hardware Configuration

16.7.2 5XX Large system Hardware Configuration

16.8 5XX IPL Performance Measurements (Normal)

16.9 5XX IPL Performance Measurements (Abnormal)

16.10 5XX IOP vs IOPLess effects on IPL Performance (Normal)

16.11 IPL Tips

17.1 Introduction

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17.2 Effects of Windows and Linux loads on the host system

17.2.1 IXS/IXA Disk I/O Operations:

17.2.2 iSCSI Disk I/O Operations:

17.2.3 iSCSI virtual I/O private memory pool

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245 246 247 247 247 248 249 249 250 251 252 253 254 255 257 258 259

260 262

263 265

267 268 270 271

273Chapter 16 IPL Performance ......................................................

273 273 274 274 274 275 275 276 276 277 277 277 278 278 279 279

280Chapter 17. Integrated BladeCenter and System x Performance .........................

280 281 281 282 283

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

17.2.4 Virtual Ethernet Connections:

17.2.5 IXS/IXA IOP Resource:

17.3 System i memory rules of thumb for IXS/IXA and iSCSI attached servers.

17.3.1 IXS and IXA attached servers:

17.3.2 iSCSI attached servers:

17.4 Disk I/O CPU Cost

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17.4.1 Further notes about IXS/IXA Disk Operations

17.5 Disk I/O Throughput

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17.6 Virtual Ethernet CPU Cost and Capacities

17.6.1 VE Capacity Comparisons

17.6.2 VE CPW Cost

17.6.3 Windows CPU Cost

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17.7 File Level Backup Performance

17.8 Summary

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17.9 Additional Sources of Information

18.1 Introduction

V5R3 Information V5R2 Additions General Tips V5R1 Additions

18.2 Considerations

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18.3 Performance on a 12-way system

18.4 LPAR Measurements

18.5 Summary

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19.1 Public Benchmarks (TPC-C, SAP, NotesBench, SPECjbb2000, VolanoMark)

19.2 Dynamic Priority Scheduling

19.3 Main Storage Sizing Guidelines

19.4 Memory Tuning Using the QPFRADJ System Value

19.5 Additional Memory Tuning Techniques

19.6 User Pool Faulting Guidelines

19.7 AS/400 NetFinity Capacity Planning

20.1 Adjusting Your Performance Tuning for Threads

20.2 General Performance Guidelines -- Effects of Compilation

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20.3 How to Design for Minimum Main Storage Use (especially with Java, C, C++)

Theory -- and Practice System Level Considerations Typical Storage Costs A Brief Example Which is more important? A Short but Important Tip about Data Base A Final Thought About Memory and Competitiveness

20.4 Hardware Multi-threading (HMT)

HMT Described HMT and SMT Compared and Contrasted Models With/Without HMT

20.5 POWER6 520 Memory Considerations

20.6 Aligning Floating Point Data on Power6

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284 285 285 285 285 286 287 288 289 290 291 291 292 293 293

295Chapter 18. Logical Partitioning (LPAR) ............................................

295 295 295 295 296 296 297 300 301

302Chapter 19. Miscellaneous Performance Information ..................................

302 304 307 307 308 310 311

314Chapter 20. General Performance Tips and Techniques ...............................

314 316 317 317 318 318 319 320 321 321 322 322 323 323 324 325

327Chapter 21. High Availability Performance ...........................................

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

21.1 Switchable IASP’s

21.2 Geographic Mirroring

22.1 Overview

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22.2 Merging PM for System i data into the Estimator

22.3 Estimator Access

22.4 What the Estimator is Not

A.1 Commercial Processing Workload - CPW A.2 Compute Intensive Workload - CIW

B.1 Performance Data Collection Services B.2 Batch Modeling Tool (BCHMDL).

C.1 V6R1 Additions (October 2008) C.2 V6R1 Additions (August 2008) C.3 V6R1 Additions (April 2008) C.4 V6R1 Additions (January 2008) C.5 V5R4 Additions (July 2007)

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C.6 V5R4 Additions (January/May/August 2006 and January/April 2007) C.7 V5R3 Additions (May, July, August, October 2004, July 2005)

C.7.1 IBM

~®

C.8 V5R2 Additions (February, May, July 2003)

C.8.1 iSeries Model 8xx Servers

i5 Servers

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C.8.2 Model 810 and 825 iSeries for Domino (February 2003) C.9 V5R2 Additions

C.9.1 Base Models 8xx Servers C.9.2 Standard Models 8xx Servers

C.10 V5R1 Additions

C.10.1 Model 8xx Servers C.10.2 Model 2xx Servers C.10.3 V5R1 Dedicated Server for Domino C.10.4 Capacity Upgrade on-demand Models

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C.10.4.1 CPW Values and Interactive Features for CUoD Models

C.11 V4R5 Additions

C.11.1 AS/400e Model 8xx Servers C.11.2 Model 2xx Servers C.11.3 Dedicated Server for Domino C.11.4 SB Models

C.12 V4R4 Additions

C.12.1 AS/400e Model 7xx Servers C.12.2 Model 170 Servers

C.13 AS/400e Model Sxx Servers C.14 AS/400e Custom Servers C.15 AS/400 Advanced Servers C.16 AS/400e Custom Application Server Model SB1 C.17 AS/400 Models 4xx, 5xx and 6xx Systems C.18 AS/400 CISC Model Capacities

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327 329

334Chapter 22. IBM Systems Workload Estimator ......................................

334 335 335 335

337Appendix A. CPW and CIW Descriptions ............................................

337 339

341Appendix B. System i Sizing and Performance Data Collection Tools ....................

342 343

345Appendix C. CPW and MCU Relative Performance Values for System i ..................

346 347 347 348 349 349 351 351 353 353 354 354 354 354 355 356 357 357 357 358 360 360 361 361 362 362 362 363 365 365 365 366 367 368

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

Special Notices

DISCLAIMER NOTICE

Performance is based on measurements and projections using standard IBM benchmarks in a controlled environment. This information is presented along with general recommendations to assist the reader to have a better understanding of IBM(*) products. The actual throughput or performance that any user will experience will vary depending upon considerations such as the amount of multiprogramming in the user's job stream, the I/O configuration, the storage configuration, and the workload processed. Therefore, no assurance can be given that an individual user will achieve throughput or performance improvements equivalent to the ratios stated here.

All performance data contained in this publication was obtained in the specific operating environment and under the conditions described within the document and is presented as an illustration. Performance

obtained in other operating environments may vary and customers should conduct their own testing.

Information is provided "AS IS" without warranty of any kind.

The use of this information or the implementation of any of these techniques is a customer responsibility and depends on the customer's ability to evaluate and integrate them into the customer's operational environment. While each item may have been reviewed by IBM for accuracy in a specific situation, there is no guarantee that the same or similar results will be obtained elsewhere. Customers attempting to adapt these techniques to their own environments do so at their own risk.

All statements regarding IBM future direction and intent are subject to change or withdrawal without notice, and represent goals and objectives only. Contact your local IBM office or IBM authorized reseller for the full text of the specific Statement of Direction.

Some information addresses anticipated future capabilities. Such information is not intended as a definitive statement of a commitment to specific levels of performance, function or delivery schedules with respect to any future products. Such commitments are only made in IBM product announcements. The information is presented here to communicate IBM's current investment and development activities as a good faith effort to help with our customers' future planning.

IBM may have patents or pending patent applications covering subject matter in this document. The furnishing of this document does not give you any license to these patents. You can send license inquiries, in writing, to the IBM Director of Commercial Relations, IBM Corporation, Purchase, NY

10577.

Information concerning non-IBM products was obtained from a supplier of these products, published announcement material, or other publicly available sources and does not constitute an endorsement of such products by IBM. Sources for non-IBM list prices and performance numbers are taken from publicly available information, including vendor announcements and vendor worldwide homepages. IBM has not tested these products and cannot confirm the accuracy of performance, capability, or any other claims related to non-IBM products. Questions on the capability of non-IBM products should be addressed to the supplier of those products.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

The following terms, which may or may not be denoted by an asterisk (*) in this publication, are trademarks of the IBM Corporation.

Operating System/400System/370iSeries or AS/400 i5/OS IPDSC/400 Application System/400COBOL/400OS/400 OfficeVisionRPG/400System i5 Facsimile Support/400CallPathSystem i Distributed Relational Database ArchitectureDRDAPS/2 Advanced Function PrintingSQL/400OS/2 Operational AssistantImagePlusDB2 Client SeriesVTAMAFP Workstation Remote IPL/400APPNIBM Advanced Peer-to-Peer NetworkingSystemViewSQL/DS OfficeVision/400ValuePoint400 iSeries Advanced Application ArchitectureDB2/400CICS ADSTAR Distributed Storage Manager/400ADSM/400S/370 IBM Network StationAnyNet/400RPG IV Lotus, Lotus Notes, Lotus Word Pro, Lotus 1-2-3AIX POWER4+POWER4Micro-partitioning

Systems

POWER5+POWER5POWER POWER6+POWER6Power PowerTM Systems SoftwarePowerTM Systems SoftwarePowerPC

The following terms, which may or may not be denoted by a double asterisk (**) in this publication, are trademarks or registered trademarks of other companies as follows:

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IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

Purpose of this Document

The intent of this document is to help provide guidance in terms of IBM i operating system performance, capacity planning information, and tips to obtain optimal performance on IBM i operating system. This document is typically updated with each new release or more often if needed.

This October 2008 edition of the IBM i V6.1 Performance Capabilities Reference Guide is an update to the April 2008 edition to reflect new product functions announced on October 7, 2008.

This edition includes performance information on newly announced IBM Power Systems including Power 520 and Power 550, utilizing POWER6 processor technology. This document further includes information on IBM System i 570 using POWER6 processor technology, IBM i5/OS running on IBM BladeCenter JS22 using POWER6 processor technology, recent System i5 servers (model 515, 525, and

595) featuring new user-based licensing for the 515 and 525 models and a new 2.3GHz model 595, DB2 UDB for iSeries SQL Query Engine Support, Websphere Application Server including WAS V6.1 both with the Classic VM and the IBM Technology for Java (32-bit) VM, WebSphere Host Access Transformation Services (HATS) including the IBM WebFacing Deployment Tool with HATS Technology (WDHT), PHP - Zend Core for i, Java including Classic JVM (64-bit), IBM Technology for Java (32-bit), IBM Technology for Java (64-bit) and bytecode verification, Cryptography, Domino 7, Workplace Collaboration Services (WCS), RAID6 versus RAID5 disk comparisons, new internal storage adapters, Virtual Tape, and IPL Performance.

The wide variety of applications available makes it extremely difficult to describe a "typical" workload. The data in this document is the result of measuring or modeling certain application programs in very specific and unique configurations, and should not be used to predict specific performance for other applications. The performance of other applications can be predicted using a system sizing tool such as IBM Systems Workload Estimator (refer to Chapter 22 for more details on Workload Estimator).

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

Chapter 1. Introduction

IBM System i and IBM System p platforms unified the value of their servers into a single, powerful lineup of servers based on industry leading POWER6 processor technology with support for IBM i operating system (formerly known as i5/OS), IBM AIX and Linux for Power.

Following along with this exciting unification are a number of naming changes to the formerly named i5/OS, now officially called IBM i operating system. Specifically, recent versions of the operating system are referred to by IBM i operating system 6.1 and IBM i operating system 5.4, formerly i5/OS V6R1 and i5/OS V5R4 respectively. Shortened forms of the new operating system name are IBM i 6.1, i 6.1, i V6.1 iV6R1, and sometimes simply ‘i’. As always, references to legacy hardware and software will commonly use the naming conventions of the time.

The Power 520 Express Edition is the entry member of the Power Systems portfolio, supporting both IBM i 5.4 and IBM i 6.1. The System i 570 is enhanced to enable medium and large enterprises to grow and extend their IBM i business applications more affordably and with more granularity, while offering effective and scalable options for deploying Linux and AIX applications on the same secure, reliable system.

The IBM Power 570 running IBM i offers IBM's fastest POWER6 processors in 2 to 16-way configurations, plus an array of other technology advances. It is designed to deliver outstanding price/performance, mainframe-inspired reliability and availability features, flexible capacity upgrades, and innovative virtualization technologies. New 5.0GHz and 4.4GHz POWER6 processors use the very latest 64-bit IBM POWER processor technology. Each 2-way 570 processor card contains one two-core chip (two processors) and comes with 32 MB of L3 cache and 8 MB of L2 cache.

The CPW ratings for systems with POWER6 processors are approximately 70% higher than equivalent POWER5 systems and approximately 30% higher than equivalent POWER5+ systems. For some compute-intensive applications, the new System i 570 can deliver up to twice the performance of the original 570 with 1.65 GHz POWER5 processors.

The 515 and 525 models introduced in April 2007, introduce user-based licensing for IBM i. For assistance in determining the required number of user licenses, see

ttp://www.ibm.com/systems/i/hardware/515 (model 515) or

h http://www.ibm.com/systems/i/hardware/525 (model 525). User-based licensing is not a

replacement for system sizing; instead, user-based licensing enables appropriate user connectivity to the system. Application environments require different amounts of system resources per user. See Chapter 22 (IBM Systems Workload Estimator) for assistance in system sizing.

Customers who wish to remain with their existing hardware but want to move to IBM i 6.1 may find functional and performance improvements. IBM i 6.1 continues to help protect the customer's investment while providing more function and better price/performance over previous

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

versions. The primary public performance information web site is found at:

http://www.ibm.com/systems/i/advantages/perfmgmt/index.html

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

Chapter 2. iSeries and AS/400 RISC Server Model Performance Behavior

2.1 Overview

iSeries and AS/400 servers are intended for use primarily in client/server or other non-interactive work environments such as batch, business intelligence, network computing etc. 5250-based interactive work can be run on these servers, but with limitations. With iSeries and AS/400 servers, interactive capacity can be increased with the purchase of additional interactive features. Interactive work is defined as any job doing 5250 display device I/O. This includes:

All 5250 sessions Any green screen interface Telnet or 5250 DSPT workstations 5250/HTML workstation gateway PC's using 5250 emulation Interactive program debugging PC Support/400 work station function

Note that printer work that passes through twinax media is treated as interactive, even though there is no “user interface”. This is true regardless of whether the printer is working in dedicated mode or is printing spool files from an out queue. Printer activity that is routed over a LAN through a PC print controller are not considered to be interactive.

This explanation is different than that found in previous versions of this document. Previous versions indicated that spooled work would not be considered to be interactive and were in error.

As of January 2003, 5250 On-line Transaction Processing (OLTP) replaces the term “interactive” when referencing interactive CPW or interactive capacity. Also new in 2003, when ordering a iSeries server, the customer must choose between a Standard Package and an Enterprise Package in most cases. The Standard Packages comes with zero 5250 CPW and 5250 OLTP workloads are not supported. However, the Standard Package does support a limited 5250 CPW for a system administrator to manage various aspects of the server. Multiple administrative jobs will quickly exceed this capability. The Enterprise Package does not have any limits relative to 5250 OLTP workloads. In other words, 100% of the server capacity is available for 5250 OLTP applications whenever you need it.

RUMBA/400 Screen scrapers Interactive subsystem monitors Twinax printer jobs BSC 3270 emulation 5250 emulation

5250 OLTP applications can be run after running the WebFacing Tool of IBM WebSphere Development Studio for iSeries and will require no 5250 CPW if on V5R2 and using model 800, 810, 825, 870, or 890 hardware.

2.1.1 Interactive Indicators and Metrics

Prior to V4R5, there were no system metrics that would allow a customer to determine the overall interactive feature capacity utilization. It was difficult for the customer to determine how much of the total interactive capacity he was using and which jobs were consuming interactive capacity. This got much easier with the system enhancements made in V4R5 and V5R1.

Starting with V4R5, two new metrics were added to the data generated by Collection Services to report the system's interactive CPU utilization (ref file QAPMSYSCPU). The first metric (SCIFUS) is the

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

interactive utilization - an average for the interval. Since average utilization does not indicate potential problems associated with peak activity, a second metric (SCIFTE) reports the amount of interactive utilization that occurred above threshold. Also, interactive feature utilization was reported when printing a System Report generated from Collection Services data. In addition, Management Central now monitors interactive CPU relative to the system/partition capacity.

Also in V4R5, a new operator message, CPI1479, was introduced for when the system has consistently exceeded the purchased interactive capacity on the system. The message is not issued every time the capacity is reached, but it will be issued on an hourly basis if the system is consistently at or above the limit. In V5R2, this message may appear slightly more frequently for 8xx systems, even if there is no change in the workload. This is because the message event was changed from a point that was beyond the purchased capacity to the actual capacity for these systems in V5R2.

In V5R1, Collection Services was enhanced to mark all tasks that are counted against interactive capacity (ref file QAPMJOBMI, field JBSVIF set to ‘1’). It is possible to query this file to understand what tasks have contributed to the system’s interactive utilization and the CPU utilized by all interactive tasks. Note: the system’s interactive capacity utilization may not be equal to the utilization of all interactive tasks. Reasons for this are discussed in Section 2.10, Managing Interactive Capacity.

With the above enhancements, a customer can easily monitor the usage of interactive feature and decide when he is approaching the need for an interactive feature upgrade.

2.1.2 Disclaimer and Remaining Sections

The performance information and equations in this chapter represent ideal environments. This information is presented along with general recommendations to assist the reader to have a better understanding of the iSeries server models. Actual results may vary significantly.

This chapter is organized into the following sections:

y Server Model Behavior y Server Model Differences y Performance Highlights of New Model 7xx Servers y Performance Highlights of Current Model 170 Servers y Performance Highlights of Custom Server Models y Additional Server Considerations y Interactive Utilization y Server Dynamic Tuning (SDT) y Managing Interactive Capacity y Migration from Traditional Models y Migration from Server Models y Dedicated Server for Domino (DSD) Performance Behavior

2.1.3 V5R3

Beginning with V5R3, the processing limitations associated with the Dedicated Server for Domino (DSD) models have been removed. Refer to section 2.13, “Dedicated Server for Domino Performance Behavior”, for additional information.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

2.1.4 V5R2 and V5R1

There were several new iSeries 8xx and 270 server model additions in V5R1 and the i890 in V5R2. However, with the exception of the DSD models, the underlying server behavior did not change from V4R5. All 27x and 8xx models, including the new i890 utilize the same server behavior algorithm that was announced with the first 8xx models supported by V4R5. For more details on these new models, please refer to Appendix C, “CPW, CIW and MCU Values for iSeries”.

Five new iSeries DSD models were introduced with V5R1. In addition, V5R1 expanded the capability of the DSD models with enhanced support of Domino-complementary workloads such as Java Servlets and WebSphere Application Server. Please refer to Section 2.13, Dedicated Server for Domino Performance Behavior, for additional information.

2.2 Server Model Behavior

2.2.1 In V4R5 - V5R2

Beginning with V4R5, all 2xx, 8xx and SBx model servers utilize an enhanced server algorithm that manages the interactive CPU utilization. This enhanced server algorithm may provide significant user benefit. On prior models, when interactive users exceed the interactive CPW capacity of a system, additional CPU usage visible in one or more CFINT tasks, reduces system capacity for all users including client/server. New in V4R5, the system attempts to hold interactive CPU utilization below the threshold where CFINT CPU usage begins to increase. Only in cases where interactive demand exceeds the limitations of the interactive capacity for an extended time (for example: from long-running, CPU-intensive transactions), will overhead be visable via the CFINT tasks. Highlights of this new algorithm include the following: y As interactive users exceed the installed interactive CPW capacity, the response times of those

applications may significantly lengthen and the system will attempt to manage these interactive excesses below a level where CFINT CPU usage begins to increase. Generally, increased CFINT may still occur but only for transient periods of time. Therefore, there should be remaining system capacity available for non-interactive users of the system even though the interactive capacity has been exceeded. It is still a good practice to keep interactive system use below the system interactive CPW threshold to avoid long interactive response times.

y Client/server users should be able to utilize most of the remaining system capacity even though the

interactive users have temporarily exceeded the maximum interactive CPW capacity.

y The iSeries Dedicated Server for Domino models behave similarly when the Non Domino CPW

capacity has been exceeded (i.e. the system attempts to hold Non Domino CPW capacity below the threshold where CFINT overhead is normally activated). Thus, Domino users should be able to run in the remaining system capacity available.

y With the advent of the new server algorithm, there is not a concept known as the interactive knee or

interactive cap. The system just attempts to manage the interactive CPU utilization to the level of the interactive CPW capacity.

y Dynamic priority adjustment (system value QDYNPTYADJ) will not have any effect managing the

interactive workloads as they exceed the system interactive CPW capacity. On the other hand, it won’t hurt to have it activated.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

y The new server algorithm only applies to the new hardware available in V4R5 (2xx, 8xx and SBx

models). The behavior of all other hardware, such as the 7xx models is unchanged (see section 2.2.3 Existing Model section for 7xx algorithm).

2.2.2 Choosing Between Similarly Rated Systems

Sometimes it is necessary to choose between two systems that have similar CPW values but different processor megahertz (MHz) values or L2 cache sizes. If your applications tend to be compute intensive such as Java, WebSphere, EJBs, and Domino, you may want to go with the faster MHz processors because you will generally get faster response times. However, if your response times are already sub-second, it is not likely that you will notice the response time improvements. If your applications tend to be L2 cache friendly such as many traditional commercial applications are, you may want to choose the system that has the larger L2 cache. In either case, you can use the IBM eServer Workload Estimator to help you select the correct system (see URL: http://

www.ibm.com/iseries/support/estimator ) .

2.2.3 Existing Older Models

Server model behavior applies to:

y AS/400 Advanced Servers y AS/400e servers y AS/400e custom servers y AS/400e model 150 y iSeries model 170 y iSeries model 7xx

Relative performance measurements are derived from commercial processing workload (CPW) on iSeries and AS/400. CPW is representative of commercial applications, particularly those that do significant database processing in conjunction with journaling and commitment control.

Traditional (non-server) AS/400 system models had a single CPW value which represented the maximum workload that can be applied to that model. This CPW value was applicable to either an interactive workload, a client/server workload, or a combination of the two.

Now there are two CPW values. The larger value represents the maximum workload the model could support if the workload were entirely client/server (i.e. no interactive components). This CPW value is for the processor feature of the system. The smaller CPW value represents the maximum workload the model could support if the workload were entirely interactive. For 7xx models this is the CPW value for the interactive feature of the system.

The two CPW values are NOT additive - interactive processing will reduce the system's client/server processing capability. When 100% of client/server CPW is being used, there is no CPU

available for interactive workloads. When 100% of interactive capacity is being used, there is no CPU available for client/server workloads.

For model 170s announced in 9/98 and all subsequent systems, the published interactive CPW represents the point (the "knee of the curve") where the interactive utilization may cause increased overhead on the system. (As will be discussed later, this threshold point (or knee) is at a different value for previously announced server models). Up to the knee the server/batch capacity is equal to the processor capacity (CPW) minus the interactive workload. As interactive requirements grow beyond the knee, overhead

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

grows at a rate which can eventually eliminate server/batch capacity and limit additional interactive growth. It is best for interactive workloads to execute below (less than) the knee of the curve. (However, for those models having the knee at 1/3 of the total interactive capacity, satisfactory performance can be achieved.) The following graph illustrates these points.

Model 7xx and 9/98 Model 170 CPU

CPU Distribution vs. Interactive Utilization

100

Announced Capacities Stop Here!

Available for Client/Server

Available CPU %

Knee

available overhead interactive

0 Full7/6

Fraction of Interactive CPW

Applies to: Model 170 anno un ce d in 9/98 and ALL systems announce d o n or after 2/99

Figure 2.1. Server Model behavior

The figure above shows a straight line for the effective interactive utilization. Real/customer environments will produce a curved line since most environments will be dynamic, due to job initiation, interrupts, etc.

In general, a single interactive job will not cause a significant impact to client/server performance

Microcode task CFINTn, for all iSeries models, handles interrupts, task switching, and other similar system overhead functions. For the server models, when interactive processing exceeds a threshold amount, the additional overhead required will be manifest in the CFINTn task. Note that a single interactive job will not incur this overhead.

There is one CFINTn task for each processor. For example, on a single processor system only CFINT1 will appear. On an 8-way processor, system tasks CFINT1 through CFINT8 will appear. It is possible to see significant CFINT activity even when server/interactive overhead does not exist. For example if there are lots of synchronous or communication I/O or many jobs with many task switches.

The effective interactive utilization (EIU) for a server system can be defined as the useable interactive utilization plus the total of CFINT utilization.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

2.3 Server Model Differences

Server models were designed for a client/server workload and to accommodate an interactive workload. When the interactive workload exceeds an interactive CPW threshold (the “knee of the curve”) the client/server processing performance of the system becomes increasingly impacted at an accelerating rate beyond the knee as interactive workload continues to build. Once the interactive workload reaches the maximum interactive CPW value, all the CPU cycles are being used and there is no capacity available for handling client/server tasks.

Custom server models interact with batch and interactive workloads similar to the server models but the degree of interaction and priority of workloads follows a different algorithm and hence the knee of the curve for workload interaction is at a different point which offers a much higher interactive workload capability compared to the standard server models.

For the server models the knee of the curve is approximately:

y 100% of interactive CPW for:

y iSeries model 170s announced on or after 9/98 y 7xx models

y 6/7 (86%) of interactive CPW for:

y AS/400e custom servers

y 1/3 of interactive CPW for:

y AS/400 Advanced Servers y AS/400e servers y AS/400e model 150 y iSeries model 170s announced in 2/98

For the 7xx models the interactive capacity is a feature that can be sized and purchased like any other feature of the system (i.e. disk, memory, communication lines, etc.).

The following charts show the CPU distribution vs. interactive utilization for Custom Server and pre-2/99 Server models.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

Custom Server Model

CPU Distribution vs. Interactive Utilization

100

Available for Client/Server

Knee

Available CPU

0 6/7 Full

Fraction of Interactive CPW

Applies to: AS/400e Custom Servers, AS/400e Mixed Mode Servers

Figure 2.2. Custom Server Model behavior

available CFINT interactive

Server Model

CPU Distribution vs. Interactive Utilization

100

Available for

Available CPU

Figure 2.3. Server Model behavior

Client/Server

0 1/3 Int-CPW Full Int-CPW

Fraction of Interactive CPW

Applies to: AS/400 Advanced Servers, AS/400e servers,

Model 150, Model 170s announced in 2/98

Knee

available CFINT interactive

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

2.4 Performance Highlights of Model 7xx Servers

7xx models were designed to accommodate a mixture of traditional “green screen” applications and more intensive “server” environments. Interactive features may be upgraded if additional interactive capacity is required. This is similar to disk, memory, or other features.

Each system is rated with a processor CPW which represents the relative performance (maximum capacity) of a processor feature running a commercial processing workload (CPW) in a client/server environment. Processor CPW is achievable when the commercial workload is not constrained by main storage or DASD.

Each system may have one of several interactive features. Each interactive feature has an interactive CPW associated with it. Interactive CPW represents the relative performance available to perform host-centric (5250) workloads. The amount of interactive capacity consumed will reduce the available processor capacity by the same amount. The following example will illustrate this performance capacity interplay:

Model 7xx and 9/98 Model 170

CPU Distribution vs. Interactive Utilization

Model 7xx Processor FC 206B (240 / 70 CPW)

100

Available for Client/Server

Available CPU %

Knee

29.2%

Announced Capacities Stop Here!

available CFINT interactive

34%

0 20 40 60 80 100 117

% of Published Interactive CPU

Applies to: Mo del 170 announced in 9/98 and ALL systems announced on or after 2/99

Figure 2.4. Model 7xx Utilization Example

(7/6)

At 110% of percent of the published interactive CPU, or 32.1% of total CPU, CFINT will use an additional 39.8% (approximate) of the total CPU, yielding an effective interactive CPU utilization of approximately 71.9%. This leaves approximately 28.1% of the total CPU available for client/server work. Note that the CPU is completely utilized once the interactive workload reaches about 34%. (CFINT would use approximately 66% CPU). At this saturation point, there is no CPU available for client/server.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

2.5 Performance Highlights of Model 170 Servers

iSeries Dedicated Server for Domino models will be generally available on September 24, 1999. Please refer to Section 2.13, iSeries Dedicated Server for Domino Performance Behavior, for additional

information.

Model 170 servers (features 2289, 2290, 2291, 2292, 2385, 2386 and 2388) are significantly more powerful than the previous Model 170s announced in Feb. '98. They have a faster processor (262MHz vs. 125MHz) and more main memory (up to 3.5GB vs. 1.0GB). In addition, the interactive workload balancing algorithm has been improved to provide a linear relationship between the client/server (batch) and published interactive workloads as measured by CPW.

The CPW rating for the maximum client/server workload now reflects the relative processor capacity rather than the "system capacity" and therefore there is no need to state a "constrained performance" CPW. This is because some workloads will be able to run at processor capacity if they are not DASD, memory, or otherwise limited.

Just like the model 7xx, the current model 170s have a processor capacity (CPW) value and an interactive capacity (CPW) value. These values behave in the same manner as described in the Performance highlights of new model 7xx servers section.

As interactive workload is added to the current model 170 servers, the remaining available client/server (batch) capacity available is calculated as: CPW (C/S batch) = CPW(processor) - CPW(interactive) This is valid up to the published interactive CPW rating. As long as the interactive CPW workload does not exceed the published interactive value, then interactive performance and client/server (batch) workloads will be both be optimized for best performance. Bottom line, customers can use the entire

interactive capacity with no impacts to client/server (batch) workload response times.

On the current model 170s, if the published interactive capacity is exceeded, system overhead grows very quickly, and the client/server (batch) capacity is quickly reduced and becomes zero once the interactive workload reaches 7/6 of the published interactive CPW for that model.

The absolute limit for dedicated interactive capacity on the current models can be computed by multiplying the published interactive CPW rating by a factor of 7/6. The absolute limit for dedicated client/server (batch) is the published processor capacity value. This assumes that sufficient disk and memory as well as other system resources are available to fit the needs of the customer's programs, etc. Customer workloads that would require more than 10 disk arms for optimum performance should not be expected to give optimum performance on the model 170, as 10 disk access arms is the maximum configuration. When the model 170 servers are running less than the published interactive workload, no Server Dynamic Tuning (SDT) is necessary to achieve balanced performance between interactive and client/server (batch) workloads. However, as with previous server models, a system value (QDYNPTYADJ - Server Dynamic Tuning ) is available to determine how the server will react to work requests when interactive workload exceeds the "knee". If the QDYNPTYADJ value is turned on, client/server work is favored over additional interactive work. If it is turned off, additional interactive work is allowed at the expense of low-priority client/server work. QDYNPTYADJ only affects the server when interactive requirements exceed the published interactive capacity rating. The shipped default value is for QDYNPTYADJ to be turned on.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

The next chart shows the performance capacity of the current and previous Model 170 servers.

Previous vs. Current AS/400e server 170 Performance

1200

1090

1000

800

600

400

CPW Values

200

114

2159 2160 2164 2176 2183 2289 2290 2291 2292 2385 2386 2388

Previous *

319 319

210

Current

460 460

220

115

70 70

Interactive Processor

* Unconstrained V4R2 rates

Figure 2.5. Previous vs. Current Server 170 Performance

2.6 Performance Highlights of Custom Server Models

Custom server models were available in releases V4R1 through V4R3. They interact with batch and interactive workloads similar to the server models but the degree of interaction and priority of workloads is different, and the knee of the curve for workload interaction is at a different point. When the interactive workload exceeds approximately 6/7 of the maximum interactive CPW (the knee of the curve), the client/server processing performance of the system becomes increasingly impacted. Once the interactive workload reaches the maximum interactive CPW value, all the CPU cycles are being used and there is no capacity available for handling client/server tasks.

2.7 Additional Server Considerations

It is recommended that the System Operator job run at runpty(9) or less. This is because the possibility exists that runaway interactive jobs will force server/interactive overhead to their maximum. At this point it is difficult to initiate a new job and one would need to be able to work with jobs to hold or cancel runaway jobs.

You should monitor the interactive activity closely. To do this take advantage of PM/400 or else run Collection Services nearly continuously and query monitor data base each day for high interactive use

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

and higher than normal CFINT values. The goal is to avoid exceeding the threshold (knee of the curve) value of interactive capacity.

2.8 Interactive Utilization

When the interactive CPW utilization is beyond the knee of the curve, the following formulas can be used to determine the effective interactive utilization or the available/remaining client/server CPW. These

equations apply to all server models.

CPWcs(maximum) = client/server CPW maximum value CPWint(maximum) = interactive CPW maximum value CPWint(knee) = interactive CPW at the knee of the curve CPWint = interactive CPW of the workload

X is the ratio that says how far into the overhead zone the workload has extended: X = (CPWint - CPWint(knee)) / (CPWint(maximum) - CPWint(knee))

EIU = Effective interactive utilization. In other words, the free running, CPWint(knee), interactive plus the combination of interactive and overhead generated by X. EIU = CPWint(knee) + (X * (CPWcs(maximum) - CPWint(knee)))

CPW remaining for batch = CPWcs(maximum) - EIU

Example 1:

A model 7xx server has a Processor CPW of 240 and an Interactive CPW of 70. The interactive CPU percent at the knee equals (70 CPW / 240 CPW) or 29.2%. The maximum interactive CPU percent (7/6 of the Interactive CPW ) equals (81.7 CPW / 240 CPW) or 34%.

Now if the interactive CPU is held to less than 29.2% CPU (the knee), then the CPU available for the System, Batch, and Client/Server work is 100% - the Interactive CPU used.

If the interactive CPU is allowed to grow above the knee, say for example 32.1 % (110% of the knee), then the CPU percent remaining for the Batch and System is calculated using the formulas above:

X = (32.1 - 29.2) / (34 - 29.2) = .604 EIU = 29.2 + (.604 * (100 - 29.2)) = 71.9%

CPW remaining for batch = 100 - 71.9 = 28.1%

Note that a swing of + or - 1% interactive CPU yields a swing of effective interactive utilization (EIU) from 57% to 87%. Also note that on custom servers and 7xx models, environments that go beyond the interactive knee may experience erratic behavior.

Example 2:

A Server Model has a Client/Server CPW of 450 and an Interactive CPW of 50. The maximum interactive CPU percent equals (50 CPW / 450 CPW) or 11%. The interactive CPU percent at the knee is 1/3 the maximum interactive value. This would equal 4%.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

Now if the interactive CPU is held to less than 4% CPU (the knee), then the CPU available for the System, Batch, and Client/Server work is 100% - the Interactive CPU used.

If the interactive CPU is allowed to grow above the knee, say for example 9% (or 41 CPW), then the CPU percent remaining for the Batch and System is calculated using the formulas above:

X = (9 - 4) / (11 - 4) = .71 (percent into the overhead area) EIU = 4 + (.71 * (100 - 4)) = 72%

CPW remaining for batch = 100 - 72 = 28%

Note that a swing of + or - 1% interactive CPU yields a swing of effective interactive utilization (EIU) from 58% to 86%.

On earlier server models, the dynamics of the interactive workload beyond the knee is not as abrupt, but because there is typically less relative interactive capacity the overhead can still cause inconsistency in response times.

2.9 Server Dynamic Tuning (SDT)

Logic was added in V4R1 and is still in use today so customers could better control the impact of interactive work on their client/server performance. Note that with the new Model 170 servers (features 2289, 2290, 2291, 2292, 2385, 2386 and 2388) this logic only affects the server when interactive requirements exceed the published interactive capacity rating. For further details see the section, Performance highlights of current model 170 servers.

Through dynamic prioritization, all interactive jobs will be put lower in the priority queue, approximately at the knee of the curve. Placing the interactive jobs at a lesser priority causes the interactive jobs to slow down, and more processing power to be allocated to the client/server processing. As the interactive jobs receive less processing time, their impact on client/server processing will be lessened. When the interactive jobs are no longer impacting client/server jobs, their priority will dynamically be raised again.

The dynamic prioritization acts as a regulator which can help reduce the impact to client/server processing when additional interactive workload is placed on the system. In most cases, this results in better overall throughput when operating in a mixed client/server and interactive environment, but it can cause a noticeable slowdown in interactive response.

To fully enable SDT, customers MUST use a non-interactive job run priority (RUNPTY parameter) value of 35 or less (which raises the priority, closer to the default priority of 20 for interactive jobs).

Changing the existing non-interactive job’s run priority can be done either through the Change Job (CHGJOB) command or by changing the RUNPTY value of the Class Description object used by the non-interactive job. This includes IBM-supplied or application provided class descriptions.

Examples of IBM-supplied class descriptions with a run priority value higher than 35 include QBATCH and QSNADS and QSYSCLS50. Customers should consider changing the RUNPTY value for QBATCH and QSNADS class descriptions or changing subsystem routing entries to not use class descriptions QBATCH, QSNADS, or QSYSCLS50.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

If customers modify an IBM-supplied class description, they are responsible for ensuring the priority value is 35 or less after each new release or cumulative PTF package has been installed. One way to do this is to include the Change Class (CHGCLS) command in the system Start Up program.

NOTE: Several IBM-supplied class descriptions already have RUNPTY values of 35 or less. In these cases no user action is required. One example of this is class description QPWFSERVER with RUNPTY(20). This class description is used by Client Access database server jobs QZDAINIT (APPC) and QZDASOINIT (TCP/IP).

The system deprioritizes jobs according to groups or "bands" of RUNPTY values. For example, 10-16 is band 1, 17-22 is band 2, 23-35 is band 3, and so on.

Interactive jobs with priorities 10-16 are an exception case with V4R1. Their priorities will not be adjusted by SDT. These jobs will always run at their specified 10-16 priority.

When only a single interactive job is running, it will not be dynamically reprioritized.

When the interactive workload exceeds the knee of the curve, the priority of all interactive jobs is decreased one priority band, as defined by the Dynamic Priority Scheduler, every 15 seconds. If needed, the priority will be decreased to the 52-89 band. Then, if/when the interactive CPW work load falls below the knee, each interactive job's priority will gradually be reset to its starting value when the job is dispatched.

If the priority of non-interactive jobs are not set to 35 or lower, SDT stills works, but its effectiveness is greatly reduced, resulting in server behavior more like V3R6 and V3R7. That is, once the knee is exceeded, interactive priority is automatically decreased. Assuming non-interactive is set at priority 50, interactive could eventually get decreased to the 52-89 priority band. At this point, the processor is slowed and interactive and non-interactive are running at about the same priority. (There is little priority difference between 47-51 band and the 52-89 band.) If the Dynamic Priority Scheduler is turned off, SDT is also turned off.

Note that even with SDT, the underlying server behavior is unchanged. Customers get no more CPU cycles for either interactive or non-interactive jobs. SDT simply tries to regulate interactive jobs once they exceed the knee of the curve.

Obviously systems can still easily exceed the knee and stay above it, by having a large number of interactive jobs, by setting the priority of interactive jobs in the 10-16 range, by having a small client/server workload with a modest interactive workload, etc. The entire server behavior is a partnership with customers to give non-interactive jobs the bulk of the CPU while not entirely shutting out interactive.

To enable the Server Dynamic Tuning enhancement ensure the following system values are on: (the shipped defaults are that they are set on)

y QDYNPTYSCD - this improves the job scheduling based on job impact on the system. y QDYNPTYADJ - this uses the scheduling tool to shift interactive priorities after the threshold is

reached.

The Server Dynamic Tuning enhancement is most effective if the batch and client/server priorities are in the range of 20 to 35.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

Server Dynamic Tuning Recommendations

On the new systems and mixed mode servers have the QDYNPTYSCD and QDYNPTYADJ system value set on. This preserves non-interactive capacities and the interactive response times will be dynamic beyond the knee regardless of the setting. Also set non-interactive class run priorities to less than 35.

On earlier servers and 2/98 model 170 systems use your interactive requirements to determine the settings. For “pure interactive” environments turn the QDYNPTYADJ system value off. in mixed environments with important non-interactive work, leave the values on and change the run priority of important non-interactive work to be less than 35.

Affects of Server Dynamic Tuning

Server Dynamic Tuning - .

High "Server" Demand

100

Knee

Available CPU

0 1/3 Int-CPW Full Int-CPW

Fraction of Interactive CPW

With sufficient batch or client/server load, Interactive is constrained to the "knee-level" by priority degradation

Interactive suffers poor response times

Available for Client/Server

available interactive

Server Dynamic Tuning

Mixed "Server" Demand

100

Knee

Available CPU

0 1/3 Int-CPW Full Int-CPW

Fraction of Interactive CPW

Without high "server" demand, Interactive allowed to grow to limit

Overhead introduced just as when Dynamic Priority Adjust is turned off

Available for Client/Server

available O.H. or Server Int. or Server interactive

Figure 2.6.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

2.10 Managing Interactive Capacity

Interactive/Server characteristics in the real world.

Graphs and formulas listed thus far work perfectly, provided the workload on the system is highly regular and steady in nature. Of course, very few systems have workloads like that. The more typical case is a dynamic combination of transaction types, user activity, and batch activity. There may very well be cases where the interactive activity exceeds the documented limits of the interactive capacity, yet decreases quickly enough so as not to seriously affect the response times for the rest of the workload. On the other hand, there may also be some intense transactions that force the interactive activity to exceed the documented limits interactive feature for a period of time even though the average CPU utilization appears to be less than these documented limits.

For 7xx systems, current 170 systems, and mixed-mode servers, a goal should be set to only rarely exceed the threshold value for interactive utilization. This will deliver the most consistent performance for both interactive and non-interactive work.

The questions that need to be answered are:

1. “How do I know whether my system is approaching the interactive limits or not?”

2. “What is viewed as ‘interactive’ by the system?”

3. “How close to the threshold can a system get without disrupting performance?”

This section attempts to answer these questions.

Observing Interactive CPU utilization

The most commonly available method for observing interactive utilization is Collection Services used in conjunction with the Performance Tools program product. The monitor collects system data as well as data for each job on the system, including the CPU consumed and the type of job. By examining the reports generated by the Performance Tools product, or by writing a query against the data in the various performance data base files.

Note: data is written to these files based on sample interval (Smallest is 5 minutes, default is 15 minutes). This data is an average for the duration of a measurement interval.

1. The first metric of interest is how much of the system’s interactive capacity has been used. The file

QAPMSYSCPU field SCIFUS contains the amount of interactive feature CPU time used. This metric became available with Collection Services in V4R5.

2. Even though average CPU may be reasonable your interactive workload may still be exceeding limits

at times. The file QAPMSYSCPU field SCIFTE contains the amount of time the interactive threshold was exceeded during the interval. This metric became available with Collection Services in V4R5.

3. To determine what jobs are responsible for interactive feature consumption, you can look at the data

in QAPMJOBL (Collection Services) or QAPMJOBS (Performance Monitor): y If using Collection Services on a V5R1 or later system, those jobs which the machine considers to

be interactive are indicated by the field JBSVIF =’1’. These are all jobs that could contribute to your interactive feature utilization.

y In all cases you can examine the jobs that are considered interactive by OS/400 as indicated by

field JBTYPE = “I”. Although not totally accurate, in most cases this will provide an adequate list of jobs that contributed to interactive utilization.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

There are other means for determining interactive utilization. The easiest of these is the performance monitoring function of Management Central, which became available with V4R3. Management Central can provide:

y Graphical, real-time monitoring of interactive CPU utilization y Creation of an alert threshold when an alert feature is turned on and the graph is highlighted y Creation of an reverse threshold below which the highlights are turned off y Multiple methods of handling the alert, from a console message to the execution of a command to the

forwarding of the alert to another system.

By taking the ratio of the Interactive CPW rating and the Processor CPW rating for a system, one can determine at what CPU percentage the threshold is reached (This ratio works for the 7xx models and the current model 170 systems. For earlier models, refer to other sections of this document to determine what fraction of the Interactive CPW rating to use.) Depending on the workload, an alert can be set at some percentage of this level to send a warning that it may be time to redistribute the workload or to consider upgrading the interactive feature.

Finally, the functions of PM400 can also show the same type of data that Collection Services shows, with the advantage of maintaining a historical view, and the disadvantage of being only historical. However, signing up for the PM400 service can yield a benefit in determining the trends of how interactive capacities are used on the system and whether more capacity may be needed in the future.

Is Interactive really Interactive?

Earlier in this document, the types of jobs that are classified as interactive were listed. In general, these jobs all have the characteristic that they have a 5250 workstation communications path somewhere within the job. It may be a 5250 data stream that is translated into html, or sent to a PC for graphical display, but the work on the iSeries is fundamentally the same as if it were communicating with a real 5250-type display. However, there are cases where jobs of type “I” may be charged with a significant amount of work that is not “interactive”. Some examples follow:

y Job initialization: If a substantial amount of processing is done by an interactive job’s initial program,

prior to actually sending and receiving a display screen as a part of the job, that processing may not be included as a part of the interactive work on the system. However, this may be somewhat rare, since most interactive jobs will not have long-running initial programs.

y More common will be parallel activities that are done on behalf of an interactive job but are not done

within the job. There are two database-related activities where this may be the case.

1. If the QQRYDEGREE system value is adjusted to allow for parallelism or the CHGQRYA command is used to adjust it for a single job, queries may be run in service jobs which are not interactive in nature, and which do not affect the total interactive utilization of the system. However, the work done by these service jobs is charged back to the interactive job. In this case, Collection Services and most other mechanisms will all show a higher sum of interactive CPU utilization than actually occurs. The exception to this is the WRKSYSACT command, which may show the current activity for the service jobs and/or the activity that they have “charged back” to the requesting jobs. Thus, in this situation it is possible for WRKSYSACT to show a lower system CPU utilization than the sum of the CPU consumption for all the jobs.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008

+ 338 hidden pages

Intel AS-400 RISC, 7xx, 170 User Manual

Table of Contents

Purpose of this Document

Chapter 1. Introduction

Chapter 2. iSeries and AS/400 RISC Server Model Performance Behavior

2.1 Overview

2.2 Server Model Behavior

2.3 Server Model Differences

2.5 Performance Highlights of Model 170 Servers

2.6 Performance Highlights of Custom Server Models

2.7 Additional Server Considerations

2.8 Interactive Utilization

2.9 Server Dynamic Tuning (SDT)

2.10 Managing Interactive Capacity