Compaq Reliable Transaction Router User Manual

ReliableTransactionRouter GettingStarted

Order Number: AA-RLE1A-TE

January 2001

This document introduces Reliable Transaction Router and describes its concepts for the system manager, system administrator, and applications programmer.

Revision/Update Information: This is a new manual. Software Version: Reliable Transaction Router Version 4.0

Compaq Computer Corporation Houston, Texas

in U. S. Patent and Trademark Ofﬁce. DECnet, OpenVMS, and PATHWORKS are trademarks of Compaq Information

Technologies Group, L.P. Microsoft and Windows NT are trademarks of Microsoft Corporation.

Intel is a trademark of Intel Corporation. UNIX and The Open Group are trademarks of The Open Group.

All other product names mentioned herein may be trademarks or registered trademarks of their respective companies.

Conﬁdential computer software. Valid license from Compaq 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.

Compaq shall not be liable for technical or editorial errors or omissions contained herein.

The information in this publication is subject to change without notice and is provided ‘‘AS IS’’ WITHOUT WARRANTY OF ANY KIND. THE ENTIRE RISK ARISING OUT OF THE USE OF THIS INFORMATION REMAINS WITH RECIPIENT. IN NO EVENT SHALL COMPAQ BE LIABLE FOR ANY DIRECT, CONSEQUENTIAL, INCIDENTAL, SPECIAL, PUNITIVE OR OTHER DAMAGES WHATSOEVER (INCLUDING WITHOUT LIMITATION, DAMAGES FOR LOSS OF BUSINESS PROFITS, BUSINESS INTERRUPTION OR LOSS OF BUSINESS INFORMATION), EVEN IF COMPAQ HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. THE FOREGOING SHALL APPLY REGARDLESS OF THE NEGLIGENCE OR OTHER FAULT OF EITHER PARTY AND REGARDLESS OF WHETHER SUCH LIABILITY SOUNDS IN CONTRACT, NEGLIGENCE, TORT OR ANY OTHER THEORY OF LEGAL LIABILITY, AND NOTWITHSTANDING ANY FAILURE OF ESSENTIAL PURPOSE OF ANY LIMITED REMEDY.

The limited warranties for Compaq products are exclusively set forth in the documentation accompanying such products. Nothing herein should be construed as constituting a further or additional warranty.

This document was prepared using VAX DOCUMENT, Version 2.1.

Contents

Preface ..................................................... vii

1 Introduction

Reliable Transaction Router . . ........................... 1–1

RTR Continuous Computing Concepts . . ................... 1–2

RTR Terminology . . ................................... 1–3

RTR Server Types . ................................... 1–15

RTR Networking Capabilities ........................... 1–23

2 Architectural Concepts

The Three-Layer Model ................................ 2–1

RTR Facilities Bridge the Gap ........................... 2–3

Broadcasts .......................................... 2–3

Flexibility and Growth ................................. 2–3

Transaction Integrity .................................. 2–4

The Partitioned Data Model . . ........................... 2–5

Object-Oriented Programming ........................... 2–5

Objects .......................................... 2–7

Messages ........................................ 2–8

Class Relationships ................................ 2–8

Polymorphism . ................................... 2–9

Object Implementation Beneﬁts ....................... 2–9

XA Support ......................................... 2–10

iii

3 Reliability Features

Servers . . ........................................... 3–1

Failover and Recovery ................................. 3–2

Router Failover ................................... 3–2

Recovery Scenarios . ................................... 3–2

Backend Recovery ................................. 3–3

Router Recovery .................................. 3–3

Frontend Recovery ................................ 3–3

4 RTR Interfaces

RTR Management Station . . . ........................... 4–2

RTR Command Line Interface ........................ 4–2

Browser Interface .................................. 4–7

Application Programming Interfaces . . . ................... 4–7

RTR Object-Oriented Programming Interface . . .......... 4–7

RTR C Programming Interface ....................... 4–9

5 The RTR Environment

The RTR System Management Environment ................ 5–1

Monitoring RTR ................................... 5–4

Transaction Management . ........................... 5–4

Partition Management . . . ........................... 5–5

The RTR Runtime Environment ......................... 5–5

What’s Next? ........................................ 5–7

Glossary

Index

Examples

2–1 Objects-Deﬁned Sample . . ........................... 2–8

Figures

1 RTR Reading Path ................................. x

1–1 Client Symbol . ................................... 1–4

1–2 Server Symbol . ................................... 1–5

1–3 Roles Symbols . ................................... 1–6

1–4 Facility Symbol ................................... 1–6

1–5 Components in the RTR Environment .................. 1–7

1–6 Two-Tier Client/Server Environment ................... 1–9

1–7 Three-Tier Client/Server Environment .................. 1–9

1–8 Browser Applet Conﬁguration ........................ 1–10

1–9 RTR with Browser, Single Node, and Database . .......... 1–11

1–10 RTR Deployed on Two Nodes ......................... 1–11

1–11 RTR Deployed on Three Nodes ....................... 1–12

1–12 Standby Server Conﬁguration ........................ 1–13

1–13 Transactional Shadowing Conﬁguration ................. 1–14

1–14 Two Sites: Transactional and Disk Shadowing with Standby

Servers .......................................... 1–15

1–15 Standby Servers ................................... 1–17

1–16 Shadow Servers ................................... 1–18

1–17 Concurrent Servers ................................ 1–19

1–18 A Callout Server .................................. 1–20

1–19 Bank Partitioning Example .......................... 1–21

1–20 Standby with Partitioning ........................... 1–23

2–1 The Three Layer Model . . ........................... 2–2

2–2 Partitioned Data Model . . ........................... 2–6

4–1 RTR Browser Interface . . ........................... 4–8

5–1 RTR System Management Environment ................ 5–3

5–2 RTR Runtime Environment .......................... 5–6

Tables

2–1 Functional and Object-Oriented Programming Compared . . . 2–7

Purpose of this Document

The goal of this document is to assist an experienced system manager, system administrator, or application programmer to understand the Reliable Transaction Router (RTR) product.

Document Structure

This document contains the following chapters:

• Chapter 1, Introduction to RTR, provides information on RTR technology, basic RTR concepts, and RTR terminology.

• Chapter 2, Architectural Concepts, introduces the RTR three-layer model and explains ths use of RTR functions and programming capabilities.

• Chapter 3, Reliability Features, highlights RTR server types and failover and recovery scenarios.

• Chapter 4, RTR Interfaces, introduces the management and programming interfaces of RTR.

Preface

• Chapter 5, The RTR Environment, describes the RTR system management and runtime environments, and provides explicit pointers to further reading in the RTR documentation set.

vii

Related Documentation

Additional resources in the RTR documentation kit include:

Document Content

For all users:

Reliable Transaction Router Release Notes

RTR Commands Lists all RTR commands, their

For the system manager:

Reliable Transaction Router Installation

Guide

Reliable Transaction Router System

Manager’s Manual

Reliable Transaction Router Migration

Guide

For the application programmer:

Reliable Transaction Router Application

Design Guide

Reliable Transaction Router C++

Foundation Classes

Reliable Transaction Router C Application

Programmer’s Reference Manual

Describes new features, changes, and known restrictions for RTR.

qualiﬁers and defaults.

Describes how to install RTR on all supported platforms.

Describes how to conﬁgure, manage, and monitor RTR.

Explains how to migrate from RTR Version 2 to RTR Version 3 (OpenVMS only).

Describes how to design application programs for use with RTR, illustrated with both the C and C++ interfaces.

Describes the object-oriented C++ interface that can be used to implement RTR object-oriented applications.

Explains how to design and code RTR applications using the C programming language; contains full descriptions of the basic RTR API calls.

viii

You can ﬁnd additional information on RTR and existing implementations on the RTR web site at http://www.compaq.com/rtr/.

Reader’s Comments

Compaq welcomes your comments on this guide. Please send your comments and suggestions by email to rtrdoc@compaq.com. Please include the document title, date from title page, order number, section and page numbers in your message. For product information, send email to rtr@compaq.com.

Conventions

This manual adopts the following conventions:

Convention Description

New term New terms are shown in bold when

User input

Terms and titles Terms deﬁned only in the glossary are

FE RTR frontend TR RTR transaction router or router BE RTR backend

introduced and deﬁned. All RTR terms are deﬁned in the glossary at the end of this document or in the supplemental glossary in the RTR Application Design Guide.

User input and programming examples are shown in a monospaced font. Boldface monospaced font indicates user input.

shown in italics when presented for the ﬁrst time. Italics are also used for titles of manuals and books, and for emphasis.

Reading Path

The reading path to follow when using the Reliable Transaction Router information set is shown in Figure 1.

Cover letter

Figure 1 RTR Reading Path

SPD Release

Notes

Getting Started

System Manager

Installation Guide

System Manager's Manual

Commands

If V2 to V3

Migration Guide

Application Programmer

Application Design Guide

If C++

C Application Programmer's Reference Manual

C++ Foundation Classes

= Tutorial

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This document introduces RTR and describes RTR concepts. It is intended for the system manager or administrator and for the application programmer who is developing an application that works with Reliable Transaction Router (RTR).

Reliable Transaction Router

Reliable Transaction Router (RTR) is failure-tolerant transactional messaging middleware used to implement large, distributed applications with client/server technologies. RTR helps ensure business continuity across multivendor systems and helps maximize uptime.

Introduction

Interoperability

Networking

You use the architecture of RTR to ensure high availability and transaction completion. RTR supports applications that run on different hardware and different operating systems. RTR also works with several database products including Oracle, Microsoft Access, Microsoft SQL Server, Sybase, and Informix. For speciﬁcs on operating systems, operating system versions, and supported hardware, see the Reliable Transaction Router Software Product Description for each supported operating system.

RTR can be deployed in a local or wide area network and can use either TCP/IP or DECnet for its underlying network transport.

Introduction 1–1

RTR Continuous Computing Concepts

RTR provides a continuous computing environment that is particularly valuable in ﬁnancial transactions, for example in banking, stock trading, or passenger reservations systems. RTR satisﬁes many requirements of a continuous computing environment:

• Reliability

• Failure tolerance

• Data and transaction integrity

• Scalability

• Ease of building and maintaining applications

• Interoperability with multiple operating systems

RTR additionally provides the following capabilities, essential in the demanding transaction processing environment:

• Flexibility

1–2 Introduction

• Parallel execution at the transaction level

• Potential for step-by-step growth

• Comprehensive monitoring tools

• Management station for single console system management

• WAN deployability

RTR also ensures that transactions have the ACID properties. A transaction with the ACID properties has the following attributes:

• Atomic

• Consistent

• Isolated

• Durable

For more details on transactional ACID properties, see the discussion later in this document, and in the RTR Application Design Guide.

RTR Terminology

The following terms are either unique to RTR or redeﬁned when used in the RTR context. If you have learned any of these terms in other contexts, take the time to assimilate their meaning in the RTR environment. The terms are described in the following order:

• Application

• Client, client application

• Server, server application

• Channel

• RTR conﬁguration

• Roles

• Frontend

• Router

• Backend

RTR Terminology

• Facility

• Transaction

• Transactional messaging

• Nontransactional messaging

• Transaction ID

• Transaction controller

• Standby server

• Transactional shadowing

• RTR journal

• Partition

• Key range

Introduction 1–3

RTR Terminology

RTR Application

Client

An RTR application is user-written software that executes within the conﬁnes of several distributed processes. The RTR application may perform user interface, business, and server logic tasks and is written in response to some business need. An RTR application can be written in any language, commonly C or C++, and includes calls to RTR. RTR applications are composed of two kinds of actors, client applications and server applications. An application process is shown in diagrams as an oval, open for a client application, ﬁlled for a server application.

A client is always a client application, one that initiates and demarcates a piece of work. In the context of RTR, a client must run on a node deﬁned to have the frontend role. Clients typically deal with presentation services, handling forms input, screens, and so on. A client could connect to a browser running a browser applet or be a webserver acting as a gateway. In other contexts, a client can be a physical system, but in RTR and in this document, physical clients are called frontends or nodes. You can have more than one instance of a client on a node.

Figure 1–1 Client Symbol

Server

1–4 Introduction

A server is always a server application, one that reacts to a client’s units of work and carries them through to completion. This may involve updating persistent storage such as a database ﬁle, toggling a switch on a device, or performing another predeﬁned task. In the context of RTR, a server must run on a node deﬁned to have the backend role. In other contexts, a server can be a physical system, but in RTR and in this document, physical servers are called backends or nodes. You can have more than one instance of a server on a node. Servers can have partition states such as primary, standby, or shadow.

Figure 1–2 Server Symbol

RTR Terminology

Channel

RTR conﬁguration

Roles

RTR expects client and server applications to identify themselves before they request RTR services. During the identiﬁcation process, RTR provides a tag or handle that is used for subsequent interactions. This tag or handle is called an RTR channel.A channel is used by client and server applications to exchange units of work with the help of RTR. An application process can have one or more client or server channels.

An RTR conﬁguration consists of nodes that run RTR client and server applications. An RTR conﬁguration can run on several operating systems including OpenVMS, Tru64 UNIX, and Windows NT among others (for the full set of supported operating systems, see the title page of this document, and the appropriate SPD). Nodes are connected by network links.

A node that runs client applications is called a frontend (FE), or is said to have the frontend role. A node that runs server applications is called a backend (BE). Additionally, the transaction router (TR) contains no application software but acts as a trafﬁc cop between frontends and backends, routing transactions to the appropriate destinations. The router also eliminates any need for frontends and backends to know about each other in advance. This relieves the application programmer from the need to be concerned about network conﬁguration details.

Introduction 1–5

RTR Terminology

Figure 1–3 Roles Symbols

Facility

The mapping between nodes and roles is done using a facility. An RTR facility is the user-deﬁned name for a particular conﬁguration whose deﬁnition provides the role-to-node map for a given application. Nodes can share several facilities. The role of a node is deﬁned within the scope of a particular facility. The router is the only role that knows about all three roles. A router can run on the same physical node as the frontend or backend, if that is required by conﬁguration constraints, but such a setup would not take full advantage of failover characteristics.

Figure 1–4 Facility Symbol

A facility name is mapped to speciﬁc physical nodes and their roles using the CREATE FACILITY command.

Figure 1–5 shows the logical relationship between client application, server application, frontends (FEs), routers (TRs), and backends (BEs) in the RTR environment. The database is represented by the cylinder. Two facilities are shown (indicated by the large double-headed arrows), the user accounts facility and the general ledger facility. The user accounts facility uses three nodes, FE, TR, and BE, while the general ledger facility uses only two, TR and BE.

1–6 Introduction

Clients send messages to servers to ask that a piece of work be done. Such requests may be bundled together into transactions. An RTR transaction consists of one or more messages that have been grouped together by a client application, so that the work done as a result of each message can be undone completely, if some part of that work cannot be done. If the system fails or is

Figure 1–5 Components in the RTR Environment

User Accounts Facility

FE TR BE

Client

application

General Ledger Facility

Server

application

disconnected before all parts of the transaction are done, then the transaction remains incomplete.

RTR Terminology

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Transaction

Transactional messaging

A transaction is a piece of work or group of operations that must be executed together to perform a consistent transformation of data. This group of operations can be distributed across many nodes serving multiple databases. Applications use services that RTR provides.

RTR provides transactional messaging in which transactions are enclosed in messages controlled by RTR.

Transactional messaging ensures that each transaction is complete, and not partially recorded. For example, a transaction or business exchange in a bank account might be to move money from a checking account to a savings account. The complete transaction is to remove the money from the checking account and add it to the savings account.

A transaction that transfers funds from one account to another consists of two individual updates: one to debit the ﬁrst account, and one to credit the second account. The transaction is not complete until both actions are done. If a system performing this work goes down after the money has been debited from the checking account but before it has been credited to the savings account, the transaction is incomplete. With transactional

Introduction 1–7

RTR Terminology

messaging, RTR ensures that a transaction is ‘‘all or nothing’’— either fully completed or discarded; either both the checking account debit and the savings account credit are done, or the checking account debit is backed out and not recorded in the database. RTR transactions have the ACID properties.

Nontransactional messaging

Transaction ID

Transaction Controller

An application will also contain nontransactional tasks such as writing diagnostic trace messages or sending a broadcast message about a change in a stock price after a transaction has been completed.

Every transaction is identiﬁed on initiation with a transaction identiﬁer or transaction ID, with which it can be logged and tracked.

To reinforce the use of these terms in the RTR context, this section brieﬂy reviews other uses of conﬁguration terminology.

A traditional two-tier client/server environment is based on hardware that separates application presentation and business logic (the clients) from database server activities. The client hardware runs presentation and business logic software, and server hardware runs database or data manager (DM) software, also called resource managers (RM). This type of conﬁguration is illustrated in Figure 1–6. (In all diagrams, all lines are bidirectional.)

With the C++ API, the Transaction Controller manages transactions (one at a time), channels, messages, and events.

Further separation into three tiers is achieved by separating presentation software from business logic on two systems, and retaining a third physical system for interaction with the database. This is illustrated in Figure 1–7.

1–8 Introduction

RTR extends the three-tier model based on hardware to a multitier, multilayer, or multicomponent software model.

Figure 1–6 Two-Tier Client/Server Environment

RTR Terminology

Application Presentation

and Business Logic

(ODBC Model)

Figure 1–7 Three-Tier Client/Server Environment

Presentation/

User Interface

Application Server/

Business Logic

Database Server

RTR provides a multicomponent software model where clients running on frontends, routers, and servers running on backends cooperate to provide reliable service and transactional integrity. Application users interact with the client (presentation layer) on the frontend node that forwards messages to the current router. The router in turn routes the messages to the current, appropriate backend, where server applications reside, for processing. The connection to the current router is maintained until the current router fails or connections to it are lost.

Database Server

LKG-11204-98WI

Server

Database

Application

LKG-11205-98WI

Introduction 1–9

RTR Terminology

All components can reside on a single node but are typically deployed on different nodes to achieve modularity, scalability, and redundancy for availability. With different systems, if one physical node goes down or off line, another router and backend node takes over. In a slightly different conﬁguration, you could have an application that uses an external applet running on a browser that connects to a client running on the RTR frontend. Such a conﬁguration is shown in Figure 1–8.

Figure 1–8 Browser Applet Conﬁguration

PC Browser

Applet

Web Server

RTR Frontend

Process

RTR Client Application

1–10 Introduction

LKG-11206-98WI

The RTR client application could be an ASP (Active Server Page) script or a process interfacing to the webserver through a standard interface such as CGI (Common Gateway Interface).

RTR provides automatic software failure tolerance and failure recovery in multinode environments by sustaining transaction integrity in spite of hardware, communications, application, or site failures. Automatic failover and recovery of service can exploit redundant or underutilized hardware and network links.

As you modularize your application and distribute its components on frontends and backends, you can add new nodes, identify usage bottlenecks, and provide redundancy to increase availability. Adding backend nodes can help divide the transactional load and distribute it more evenly. For example, you could have a single node conﬁguration as shown in Figure 1–9, RTR with Browser, Single Node, and Database. A

single node conﬁguration can be useful during development, but would not normally be used when your application is deployed.

Figure 1–9 RTR with Browser, Single Node, and Database

Browser

RTR Terminology

When creating the conﬁguration used by an application and deﬁning the nodes where a facility has its frontends, routers, and backends, the setup must also deﬁne which nodes will have journal ﬁles. Each backend in an RTR conﬁguration must have a journal ﬁle to capture transactions when other nodes are unavailable. When applications are deployed, often the backend is separated from the frontend and router, as shown in Figure 1–10.

Figure 1–10 RTR Deployed on Two Nodes

Browser

Client

TR BE

LKG-11207-98WI

Server

Journal

LKG-11208-98WI

Introduction 1–11

RTR Terminology

In this example, the frontend with the client and the router reside on one node, and the server resides on the backend. Frequently, routers are placed on backends rather than on frontends. A further separation of workload onto three nodes is shown in Figure 1–11.

Figure 1–11 RTR Deployed on Three Nodes

Browser

LKG-11209-98WI

This three-node conﬁguration separates transaction load onto three nodes, but does not provide for continuing work if one of the nodes fails or becomes disconnected from the others. In many applications, there is a need to ensure that there is a server always available to access the database.

In this case, a standby server will do the job. A standby server (see Figure 1–12 is a process that can take over when the primary server is not available. Both the primary and the standby server access the same database, but the primary processes all transactions unless it is unavailable. The standby processes transactions only when the primary is unavailable. At other times, the standby can do other work. The standby server is often placed on a node other than the node where the primary server runs.

1–12 Introduction

Figure 1–12 Standby Server Conﬁguration

Server

Primary

Server

Standby

Server

RTR Terminology

LKG-11210-98WI

Transactional shadowing

RTR Journal

To increase transaction availability, transactions can be shadowed with a shadow server. This is called transactional shadowing and is accomplished by having a second location, often at a different site, where transactions are also recorded. This is illustrated in Figure 1–13. Data are recorded in two separate data stores or databases. The router knows about both backends and sends all transactions to both backends. RTR provides the server application with the necessary information to keep the two databases synchronized.

In the RTR environment, one data store (database or data ﬁle) is elected the primary, and a second data store is made the shadow. The shadow data store is a copy of the data store kept on the primary. If either data store becomes unavailable, all transactions continue to be processed and stored on the surviving data store. At the same time, RTR makes a record of (remembers) all transactions stored only on the shadow data store in the RTR journal by the shadow server. When the primary server and data store become available again, RTR replays the transactions in the journal to the primary data store through the primary server. This brings the data store back into synchronization.

Introduction 1–13

RTR Terminology

Figure 1–13 Transactional Shadowing Conﬁguration

Server

Primary

Server

With transactional shadowing, there is no requirement that hardware, the data store, or the operating system at different sites be the same. You could, for example, have one site running OpenVMS and another running Windows NT; the RTR transactional commit process would be the same at each site.

Transactional shadowing shadows only transactions controlled by RTR.

For full redundancy to assure maximum availability, a conﬁguration could employ both disk shadowing in clusters at separate sites coupled with transactional shadowing across sites with standby servers at each site. This conﬁguration is shown in Figure 1–14. For clarity, not all possible connections are shown. In the ﬁgure, backends running standby servers are shaded, connected to routers by dashed lines. Only one site (the upper site) does full disk shadowing; the lower site is the shadow for transactions, shadowing all transactions being done at the upper site.

Shadow

Server

LKG-11211-98WI

Note

1–14 Introduction

RTR Server Types

Figure 1–14 Two Sites: Transactional and Disk Shadowing with Standby Servers

Standby Server or Router

Disk

Shadowing

Transactional

Shadowing

LKG-11212-98WI

RTR Server Types

In the RTR environment, in addition to the placement of frontends, routers, and servers, the application designer must determine what server capabilities to use. RTR provides four types of software servers for application use:

• Standby servers

• Transactional shadow servers

Introduction 1–15

RTR Server Types

• Concurrent servers

• Callout servers

These are described in the next few paragraphs. You specify server types to your application in RTR API calls.

RTR server types help to provide continuous availability and a secure transactional environment.

Standby server

Standby in a cluster

The standby server remains idle while the RTR primary backend server performs its work, accepting transactions and updating the database. When the primary server fails, the standby server takes over, recovers any in-progress transactions, updates the database, and communicates with clients until the primary server returns. There can be many instances of a standby server. Activation of the standby server is transparent to the user.

A typical standby conﬁguration is shown in Figure 1–12, Standby Server Conﬁguration. Both physical servers running the RTR backend software are assumed by RTR to connect to the same database. The primary server is typically in use, and the standby server can be either idle or used for other applications, or data partitions, or facilities. When the primary server becomes unavailable, the standby server takes over and completes transactions as shown by the dashed line. Primary server failure could be caused by server process failure or backend (node) failure.

The intended and most common use of a standby server is in a cluster environment. In a non- cluster environment, seamless failover of standbys is not guaranteed.

Standby servers are ‘‘spare’’ servers which automatically take over from the main backend if it fails. This takeover is transparent to the application.

1–16 Introduction

Figure 1–15 shows a simple standby conﬁguration. The two backend nodes are members of a cluster environment, and are both able to access the database.

For any one key range, the main or primary server (Server) runs on one node while the standby server (Standby) runs on the other node. The standby server process is running, but RTR does not pass any transactions to it. Should the primary node fail, RTR starts passing transactions to (Standby). Note that

RTR Server Types

one node can contain the primary servers for one key range and standby servers for another key range to balance the load across systems. This allows the nodes in a cluster environment to act as standby for other nodes without having idle hardware. When setting up a standby server, both servers must have access to the same journal.

Figure 1–15 Standby Servers

Transactional shadow server

Terminals

Frontends (FE) Routers (TR)

Client

Backends (BE)

Server

Standby

Database (DB)

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The transactional shadow server places all transactions recorded on the primary server on a second database. The transactional shadow server can be at the same site or at a different site, and must exist in a networked environment.

A transactional shadow server can also have standby servers for greater reliability. When one member of a shadow set fails, RTR remembers the transactions executed at the surviving site in a journal, and replays them when the failed site returns. Only after all journaled transactions are recovered does the recovering site receive new online transactions. Transactional shadowing is done by partition. A transactional shadow conﬁguration can have only two members of the shadow set.

Shadow servers are servers on separate backends which handle the same transactions in parallel on identical copies of the database.

Introduction 1–17

RTR Server Types

Figure 1–16 shows a simple shadow conﬁguration. The main (BE) Server at Site 1 and the shadow server (Shadow) at Site 2 both receive every transaction for the data partition they are servicing. Should Site 1 fail, Site 2 continues to operate without interruption. Sites can be geographically remote, for example, available at separate locations in a wide area network (WAN).

Figure 1–16 Shadow Servers

Terminals

Frontends (FE) Routers (TR)

Backends (BE)

Database (DB)

Concurrent server

Client

BE - SITE 1

Server

BE - SITE 2

Shadow

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Note that each shadow server can also have standby servers. The concurrent server is an additional instance of a server

application running on the same node. RTR delivers transactions to a free server from the pool of concurrent servers. If one server fails, the transaction in process is replayed to another server in the concurrent pool. Concurrent servers are designed primarily to increase throughput and can exploit Symmetric Multiprocessing (SMP) systems. Figure 1–17, Concurrent Servers, illustrates the use of concurrent servers sending transactions to the same partition on a backend, the partition A-N.

1–18 Introduction

Concurrent servers allow transactions to be processed in parallel to increase throughput. Concurrent servers deal with the same database partition, and may be implemented as multiple

Callout server

RTR Server Types

channels within a single process or as one channel in separate processes.

Figure 1–17 Concurrent Servers

Server1

Server2

Server3

Server4

The callout server provides message authentication on transaction requests made in a given facility, and could be used, for example, to provide audit trail logging. A callout server can run on either backend or router nodes. A callout server receives a copy of all messages in a facility. Because the callout server votes on the outcome of each transaction it receives, it can veto any transaction that does not pass its security checks.

A-N

LKG-11275-98WI

A callout server is facility based, not partition based; any message arriving at the facility is routed to both the server and the callout. A callout server is enabled when the facility is deﬁned. Figure 1–18 illustrates the use of a callout server that authenticates every transaction (txn) in a facility.

To authenticate any part of a transaction, the callout server must vote on the transaction, but does not write to the database. RTR does not replay a transaction that is only authenticated.

Introduction 1–19

RTR Server Types

Figure 1–18 A Callout Server

Authentication

Callout Server

User Accounts Facility

Application

Server

Transaction

LKG-11276-98WI

Partition A

RTR callout servers provide partition-independent processing for authentication. For example, a callout server can enable checks to be carried out on all requests in a given facility.

Callout servers run on backend or router nodes. They receive a copy of every transaction either delivered to or passing through the node.

Callout servers offer the following advantages:

• The security check can run in parallel with the database updates thus improving response times.

• The security check can be run on the router hardware.

1–20 Introduction

• The security checking code is completely separated from other application code.

Since this technique relies on backing out unauthorized transactions, it is most suitable when only a small proportion of transactions are expected to fail the security check, so as not to have a performance impact.

RTR Server Types

Partition

When working with database systems, partitioning the database can be essential to ensuring smooth and untrammeled performance with a minimum of bottlenecks. When you partition your database, you locate different parts of your database on different disk drives to spread both the physical storage of your database onto different physical media and to balance access trafﬁc across different disk controllers and drives.

For example, in a banking environment, you could partition your database by account number, as shown in Figure 1–19. A partition is a segment of your database.

Figure 1–19 Bank Partitioning Example

Appn

Server - BE

Appn

Server - BE

Appn

Server - BE

Appn

Server - BE

Appn

Server - BE

Key range

Accts 1-19,999

Accts 20,00039,999

Accts 40,00069,999

Accts 70,00089,999

Accts 90,00099,999

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Once you have decided to partition your database, you use key ranges in your application to specify how to route transactions to the appropriate database partition. A key range is the range of data held in each partition. For example, the key range for the ﬁrst partition in the bank partitioning example goes from 00001 to 19999. You can assign a partition name in your application program or have it set by the system manager. Note that sometimes the terms key range and partition are used as synonyms in code examples and samples with RTR,

Introduction 1–21

RTR Server Types

but strictly speaking, the key range deﬁnes the partition. A partition has both a name, its partition name, and an identiﬁer generated by RTR — the partition ID. The properties of a partition (callout, standby, shadow, concurrent, key segment range) can be deﬁned by the system manager with a CREATE PARTITION command. For details of the command syntax, see the RTR System Manager’s Manual.

A signiﬁcant advantage of the partitioning shown in the bank example is that you can add more account numbers without making changes to your application; you need only add another server and disk drive for the new account numbers. For example, say you need to add account numbers from 90,000 to 99,999 to the basic conﬁguration of Figure 1–19, Bank Partitioning Example. You can add these accounts and bring them on line easily. The system manager can change the key range with a command, for example, in an overnight operation, or you can plan to do this during scheduled maintenance.

A partition can also have multiple standby servers.

Standby Server Conﬁgurations

Anonymous clients

Tunnel

A node can be conﬁgured as a primary server for one key range and as a standby server for another key range. This helps to distribute the work of the standby servers. Figure 1–20 illustrates this use of standbys with distributed partitioning. As shown in Figure 1–20, Application Server A is the primary server for accounts 1 to 19,999 and Application Server B is the standby for these same accounts. Application Server B is the primary for accounts 20,000 to 39,999 and Application Server A can be the standby for these same accounts (not shown in the ﬁgure). For clarity, account numbers are shown only for primary servers and one standby server.

RTR supports anonymous clients, that is, clients can be set up in a conﬁguration using wildcarded node names.

RTR can also be used with ﬁrewall tunneling software, which supports secure internet communication for an RTR connection, either client-to-router, or router-to-backend.

1–22 Introduction

Figure 1–20 Standby with Partitioning

RTR Networking Capabilities

1-19999

Application

ServerA

Router

1-19999

20000-39999

Application

ServerB

RTR Networking Capabilities

Depending on operating system, RTR uses TCP/IP or DECnet as underlying transports for the virtual network (RTR facilities) and can be deployed in both local area and wide area networks. PATHWORKS 32 is required for DECnet conﬁgurations on Windows NT.

1-19999

20000-39999

Accounts:

1-19999

20000-39999

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Introduction 1–23

This chapter introduces concepts on basic transaction processing and RTR architecture.

The Three-Layer Model

RTR is based on a three-layer architecture consisting of frontend (FE) roles, backend (BE) roles and router (TR) roles. The roles are shown in Figure 2–1. In this and subsequent diagrams, rectangles represent physical nodes, ovals represent application software, and DB represents the disks storing the database (and usually the database software that runs on the server).

Client processes run on nodes deﬁned to have the frontend role. This layer allows computing power to be provided locally at the end-user site for transaction acquisition and presentation.

Architectural Concepts

Server processes (represented by ‘‘Server’’ in Figure 2–1) run on nodes deﬁned to have the backend role. This layer:

• Allows the database to be distributed geographically.

• Permits replication of servers to cope with either network, node or site failures.

• Allows computer resources to be added to meet performance requirements.

Architectural Concepts 2–1

The Three-Layer Model

Server

Client

Terminals

Frontends (FE) Routers (TR)

Backends (BE)

Database (DB)

Figure 2–1 The Three Layer Model

2–2 Architectural Concepts

Server

Client

ZKO-GS011-99AI

• Allows performance or geographic expansion while protecting the investments made in existing hardware and application software.

The router layer contains no application software unless running callout servers. This layer reduces the number of logical network links required on frontend and backend nodes. It also decouples the backend layer from the frontend layer so that conﬁguration changes in the (frequently changing) user environment have little inﬂuence on the transaction processing and database (backend) environment.

The three layer model can be mapped to any system topology. More than one role may be assigned to any particular node. For example, on a system with few frontends, the router and frontend layers can be combined in the same nodes. During application development and test, all three roles can be combined in one node.

The nodes used by an application and their conﬁguration roles are speciﬁed using RTR conﬁguration commands. RTR lets application code be completely location and conﬁguration independent.

RTR Facilities Bridge the Gap

Many applications can use RTR at the same time without interfering with one another. This is achieved by deﬁning a separate facility for each application.

RTR Facilities Bridge the Gap

Broadcasts

When an application calls the declare a channel as a client or server, it speciﬁes the name of the facility it will use.

See the RTR System Manager’s Manual for information on how to deﬁne facilities.

Sometimes an application has a requirement to send unsolicited messages to multiple recipients.

An example of such an application is a commodity trading system, where the clients submit orders and also need to be informed of the latest price changes.

The RTR broadcast capability meets this requirement. Recipients subscribe to a class of broadcasts; a sender broadcasts

a message in this class, all interested recipients receive the message.

RTR permits clients to broadcast messages to one or more servers, or servers to broadcast to one or more clients. If a server needs to broadcast a message to another server, it must open a second channel as a client.

rtr_open_channel( )

routine to

Flexibility and Growth

RTR allows you to cope easily with changes in:

• Network demand

Architectural Concepts 2–3

Flexibility and Growth

• User access patterns

• The volume of data

Since an RTR-based system can be built using multiple systems at each functional layer, it easily lends itself to step-by-step growth, avoiding unused capacity at each stage. With your system still up and running, it is possible to:

• Create and delete concurrent server processes.

• Add or remove nodes (frontend, router or backend).

This means you do not need to provide spare capacity to allow for growth.

RTR also allows parallel execution. This means that different parts of a single transaction can be processed in parallel by multiple servers.

RTR provides a comprehensive set of monitoring tools to help you evaluate the volume of trafﬁc passing through the system. This can help you respond to unexpected load changes by altering the system conﬁguration dynamically.

Transaction Integrity

RTR greatly simpliﬁes the design and coding of distributed applications, because, with RTR, database actions can be bundled together into transactions.

To ensure that your application deals with transactions correctly, its transactions must be:

• Atomic

• Consistent

• Isolated

• Durable

These are the ACID properties of transactions. For more detail on these properties, see the Reliable Transaction Router Application Design Guide.

2–4 Architectural Concepts

The Partitioned Data Model

One goal in designing for high transaction throughput is reducing the time that users must wait for shared resources.

While many elements of a transaction processing system can be duplicated, one resource that must be shared is the database. Users compete for a shared database in three ways:

• For use of the disk

• For locks on database records

• For the CPU resources needed to access the database

This competition can be alleviated by spreading the database across several backend nodes, each node being responsible for a subset of the data, or partition. RTR enables you to implement this partitioned data model, shown roughly in Figure 2–2 where the database has three partitions. RTR routes messages to the correct partition on the basis of an application-deﬁned key. For a more complete description of partitioning as provided with RTR, see the Reliable Transaction Router Application Design Guide.

The Partitioned Data Model

Object-Oriented Programming

The C++ foundation classes map traditional RTR functional programming concepts into an object-oriented programming model. Using the power and features of these foundation classes requires a basic understanding of the differences between functional and object-oriented programming concepts. Table 2–1 compares the worlds of functional programming and object-oriented programming.

Architectural Concepts 2–5

Object-Oriented Programming

Server

Client

Terminals

Frontends (FE) Routers (TR)

Backends (BE)

Database (DB)

Figure 2–2 Partitioned Data Model

Client

Server

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2–6 Architectural Concepts

Object-Oriented Programming

Table 2–1 Functional and Object-Oriented Programming

Compared

Functional Programming Object-Oriented Programming

Objects

A program consists of data structures and algorithms.

The basic programming unit is the function, that when run, implements an algorithm.

Functions operate on elemental data types or

A program consists of a team of cooperating objects.

The basic programming unit is the class, that when instantiated, implements an object.

Objects communicate by sending messages.

data structures. An application’s architecture

consists of a hierarchy of functions and sub-functions.

An applications architecture consists of objects that model entities of the problem domain. Objects’ relationships can vary.

In the object-oriented environment, a program or application is a grouping of cooperating objects. The basic programming unit is the class. Instantiating, or declaring an instance of, a class implements an object. RTR provides object-oriented programming capabilities with the C++ API, described in the C++ Foundation Classes manual. Objects are instances of a class. In a transaction class, each transaction is an object. An object is an instantiated (declared) class. Its state and behavior are determined by the attributes and methods deﬁned in the class. An object or class is deﬁned by its:

• State (attributes)

• Behavior (methods)

• Identity (name at instantiation)

The name given at object declaration is its identity. In Example 2–1, the two dog objects King and Fiﬁ are instances of Dog. The Dog class is declared in a header (Dog.h) ﬁle and implemented in a .cpp ﬁle.

Architectural Concepts 2–7

Object-Oriented Programming

Example 2–1 Objects-Deﬁned Sample

Dog.h: class Dog { ... }; main.cpp: #include "Dog.h" main() {

Dog King; Dog Fifi;

}

Messages

Class Relationships

Objects communicate by sending messages. This is done by calling an object’s methods.

Some principal categories of messages are:

• Constructors: Create objects

• Destructors: Delete objects

• Selectors: Return part or all of an object’s state. For example, a Get method

• Modiﬁers: Change part or all of an object’s state. For example, a Set method

• Iterators: Access multiple element objects within a container object. For example, an array.

Classes can be related in the following ways:

• Simple association: One class is aware of another class. For example, "Dog object is associated with a Master object." This is a "Knows a" relationship.

• Composition: One class contains another class as part of its attributes. For example, "Dog objects contains Leg objects." This is a "Has a" relationship.

• Inheritance A child class is derived from one or more parent, or base, classes. For example, "Mutt object derives from Collie object and Boxer object which both derive from Dog object." This is an "Is a" relationship. Inheritance enables the use of polymorphism.

2–8 Architectural Concepts

Object-Oriented Programming

Polymorphism

Object Implementation Beneﬁts

Polymorphism is the ability of objects, inherited from a common base or parent class, to respond differently to the same message. This is done by deﬁning different implementations of the same method name within the individual child class deﬁnitions. For example: A DogArray object, "DogArray OurDogs[2];" refers to two element objects of class Dog, the base class:

• King, of class Doberman, is a derived or child class of Dog.

• Fiﬁ, of class Minipoodle, is a derived or child class of Dog.

If, in a program, OurDogs[n]->Bark() is called in a loop, then:

• In iteration one ([1]), method King::Bark() is called.

• In iteration two ([2]), method Fiﬁ::Bark() is called.

King’s bark does not sound like Fiﬁ’s bark because each Bark() call is a separately deﬁned method within its child object deﬁnition. The virtual parent class (Dog) method Bark() is deﬁned in the class deﬁnition of Dog.

The beneﬁts of creating RTR solutions with C++ foundation classes include the following:

• Each major RTR concept is represented by its own individual foundation class.

• Simple methods within RTR classes transform features of RTR for streamlined solutions.

• Major classes include Get and Set methods for changing transaction states.

• Default handling code is provided for all Messages and Events, where appropriate.

• You do not need to provide handling code for all messages and events.

• The sending and receiving of data is abstracted to a higher level with transaction controller and data classes.

• No buffers and links coding is needed.

• Internal RTR information is accessible without a need to know RTR internals.

Architectural Concepts 2–9

XA Support

The XA interface is part of the X/Open DTP (Distributed Transaction Processing) standard. It deﬁnes the interface that transaction managers (TM) and resource managers (RM) use to perform the two-phase commit protocol. (Resource managers are underlying database systems such as ORACLE RDBMS, Microsoft SQL Server, and others.) This interface is not used by the application programs; it is only used by TM-to-RM exchanges to coordinate a transaction.

For details on using XA, see the RTR C Application

Programmer’s Reference Manual and the RTR Application Design Guide.

2–10 Architectural Concepts

Servers

Reliability Features

Reliability in RTR is enhanced by the use of:

• Concurrent servers

• Standby servers

• Shadow servers

• Callout servers

• Router failover

Note that, conceptually, servers can be contrasted as follows:

• Concurrent servers handle similar transactions which access the same data partition and run on the same node.

• Shadow servers handle the same transactions and run on different nodes.

• Standby servers provide a node that can take over processing on a data partition when the primary server or node fails.

• Callout servers run on backends or routers and receive all messages within a facility so that authentication and logging operations can be performed in parallel.

All servers are further described in the earlier section on RTR Terminology.

Reliability Features 3–1

Failover and Recovery

RTR provides several capabilities to ensure failover and recovery under several circumstances.

Router Failover

Backend Restart Recovery

Transaction Message Replay

Link Failure Recovery

Frontend nodes automatically connect to another router if the one being used fails. This reconnection is transparent to the application.

Routers are responsible for coordinating the two-phase commit for transactions. If the original router coordinating a transaction fails, backend nodes select another router that can ensure correct transaction completion.

Transactions in the process of being committed at the time of a failure are recovered from RTR’s disk journal. Recovery could be with a concurrent server, a standby server, or a restarted server created when the failed backend restarts.

Correct ordering of the execution of transactions against the database is maintained.

Transaction messages which are lost in transit are re-sent when possible. The frontend and backend nodes keep an in-memory copy of all active messages for this purpose.

In the event of a communications failure, RTR tries to reconnect the link or links until it succeeds.

Recovery Scenarios

This section describes how RTR recovers from different hardware and software failure. For additional information on failure and recovery scenarios, see the RTR Application Design Guide.

3–2 Reliability Features

Recovery Scenarios

Backend Recovery

Router Recovery

Frontend Recovery

If standby or shadow servers are available on another backend node, operation of the rest of the system will continue without interruption, using the standby or shadow server.

If a backend processor is lost, any transactions in progress are remembered by RTR and later recovered, either when the backend restarts, or by a standby if one is present. Thus, the distributed database is brought back to a transaction-consistent state.

If a router fails and another router node is available, all inprogress transactions are transparently re-routed by the other router. System operation will continue without interruption.

If a frontend is lost:

• All transactions committed but not completed on the frontend node at the time of failure will be completed.

• All transactions started but not committed on the frontend node at the time of failure will be aborted.

Reliability Features 3–3

RTR Interfaces

RTR provides interfaces for management and application programming.

You manage RTR with a management interface from the RTR management station. The management interfaces are:

• The command line interface or CLI

• The browser interface

The application programming interfaces (APIs) are:

• The object-oriented API for C++ programming, available with RTR Version 4.0. Use this API for all new development and, where appropriate, for new work on existing applications. An application can contain both object-oriented classes and portable API calls. This API can be used to implement applications on all platforms supported by RTR.

• The RTR API for C programming, available with RTR V3. This interface is also called the Portable API because it can be used to implement applications on all platforms supported by RTR.

• The OpenVMS API containing OpenVMS calls, available with RTR V2. This API, supported on OpenVMS only, is obsolete for new development. While applications using this API should be rewritten in the new object-oriented API to take advantage of new RTR features and capabilities, they can be changed by adding object-oriented classes rather than being rewritten.

You can use the command line interface to the API to write simple RTR applications for testing and experimentation. The CLI is described in the Reliable Transaction Router System Manager’s Manual. Its use is illustrated in this chapter.

RTR Interfaces 4–1

The RTR application programming interfaces are identical on all hardware and operating system platforms that support RTR. The object-oriented API is fully described in the manual Reliable Transaction Router C++ Foundation Classes. The Cprogramming API is fully described in the Reliable Transaction Router C Application Programmer’s Reference Manual. Both APIs are used in designs in the RTR Application Design Guide.

RTR Management Station

You can manage RTR from a node on which RTR is running, from a remote node from which you send RTR commands to a node running RTR, or from a browser. The node where you enter commands, interact with the browser, or view results is your management station.

RTR Command Line Interface

The command line interface (CLI) to the RTR API enables the programmer to write short RTR applications from the RTR command line. This can be useful for testing short program segments and exploring how RTR works. For example, the following sequence of commands starts RTR and exchanges a message between a client and a server. To use these examples, you execute RTR commands simulating your RTR client application on the frontend and commands simulating your server application on the backend.

Note

The channel identiﬁer identiﬁes the application process to the ACP. The client and server process must each have a unique channel identiﬁer. In this example, the channel identiﬁer for the client is C and for the server is S. Both use the facility called DESIGN.

The following example shows communication between a client and a server created by entering commands at a terminal keyboard. The client application is executing on the frontend and the server on the backend.

4–2 RTR Interfaces

RTR Management Station

The user is called user, the facility being deﬁned is called DESIGN, a client and a server are established, and a test

message containing the words "Kathy’s text today" is sent from the client to the server. After the server receives this text, the user on the server enters the words "And this is my response." System responses begin with the characters % RTR-. Notes on the procedure are enclosed in square brackets [ ]. For clarity, commands you enter are shown in bold. You can view the status of a transaction with the SHOW TRANSACTION command.

The exchange of messages you observe in executing these commands illustrates RTR activity. You need to retain a similar sequence in your own designs for starting up RTR and initiating your own application.

You can use RTR SHOW and MONITOR commands to display status and examine system state at any time from the CLI. For more information on RTR commands, see the Reliable Transaction Router System Manager’s Manual.

Note

The

rtr_receive_message

if no message is currently available. When using the

rtr_receive_message

/TIME=0 qualiﬁer or TIMEOUT to poll for a message, if you do not want your block.

command waits or blocks

command in the RTR CLI, use the

rtr_receive_message

command to

RTR Interfaces 4–3

RTR Management Station

[The user issues the following commands on the server application where RTR is running on the backend.]

$ RTR Copyright Compaq Computer Corporation 1994. RTR> set mode/group %RTR-I-STACOMSRV, starting command server on node NODEA %RTR-I-GRPMODCHG, group changed from " " to "username" %RTR-I-SRVDISCON, server disconnected on node NODEA RTR> CREATE JOURNAL %RTR-I-STACOMSRV, starting command server on node NODEA in group "username" %RTR-S-JOURNALINI, journal has been created on device D: RTR> SHOW JOURNAL Journal configuration on NODEA in group "username" at Mon Aug 28 14:54:11 2000:-

Disk: D:\ Blocks: 1000 RTR> start rtr

%RTR-I-NOLOGSET, logging not set %RTR-S-RTRSTART, RTR started on node NODEA in group "username" RTR> CREATE FACILITY DESIGN/ALL_ROLES=(NODEA)

[- or /all=NODEA,NODEB]

%RTR-S-FACCREATED, facility DESIGN created RTR> SHOW FACILITY Facilities on node NODEA in group "username" at Mon Aug 28 15:00:28 2000: Facility Frontend Router Backend DESIGN yes yes yes RTR> rtr_open/server/accept_explicit/prepare_explicit/chan=s/fac=DESIGN %RTR-S-OK, normal successful completion RTR> RTR_RECEIVE_MESSAGE/CHAN=S %RTR-S-OK, normal successful completion

channel name: S

. . . msgtype: rtr_mt_opened . . . status: normal successful completion

4–4 RTR Interfaces

[When the next command is issued, RTR waits for a message from the client.]

RTR Management Station

RTR> RTR_RECEIVE_MESSAGE/CHAN=S %RTR-S-OK, normal successful completion

channel name: S

msgsb

msgtype: rtr_mt_msg1 msglen: 19 usrhdl: 0

Tid: 63b01d10,0,0,0,0,2e59,43ea2002

message

offset bytes text 000000 4B 61 74 68 79 27 73 20 74 65 78 74 20 74 6F 64 Kathy’s text tod 000010 61 79 00 ay. reason: Ox00000000

RTR> RTR_REPLY_TO_CLIENT/CHAN=S "And this is my response." %RTR-S-OK, normal successful completion RTR> show transaction Frontend transactions on node NodeA in group "username" at Mon Aug 28 15:12:10 2000 Tid Facility FE-User State 63b01d10,0,0,0,0,2e59,43ea2002 DESIGN username. SENDING Router transactions on node NodeA in group "username" at Mon Aug 28 15:12:10 2000: 63b01d10,0,0,0,0,2e59,43ea2002 DESIGN username. SENDING Backend transactions on node NodeA in group "username" at Mon Aug 28 15:12:10 2000: 63b01d10,0,0,0,0,2e59,43ea2002 DESIGN username. RECEIVING RTR> RTR_RECEIVE_MESSAGE/CHAN=S %RTR-S-OK, normal successful completion

channel name: S

msgsb

msgtype: rtr_mt_prepare

[if OK, use: RTR_ACCEPT_TX else, use: RTR_REJECT_TX]

RTR> RTR_RECEIVE_MESSAGE/TIME=0 RTR> STOP RTR [Ends example test.]

[Commands and system response at client.]

$ RTR RTR> START RTR %RTR-S-RTRSTART, RTR started on node NODEA in group "username"

RTR> RTR_OPEN_CHANNEL/CHANNEL=C/CLIENT/fac=DESIGN %RTR-S-OK, normal successful completion

RTR Interfaces 4–5

RTR Management Station

RTR> RTR_RECEIVE_MESSAGE/CHANNEL=C/tim

[to get mt_opened or mt_closed]

%RTR-S-OK, normal successful completion

channel name: C

msgsb

msgtype: rtr_mt_opened msglen: 8

message

status: normal successful completion reason: Ox00000000

RTR> RTR_START_TX/CHAN=C %RTR-S-OK, normal successful completion RTR> RTR_SEND_TO_SERVER/CHAN=C "Kathy’s text today." [text sent to the server] %RTR-S-OK, normal successful completion RTR> show transaction Frontend transactions on node NodeA in group "username" at Mon Aug 28 15:05:43 2000 Tid Facility FE-User State 63b01d10,0,0,0,0,2e59,43ea2002 DESIGN username. SENDING Router transactions on node NodeA in group "username" at Mon Aug 28 15:06:43 2000: 63b01d10,0,0,0,0,2e59,43ea2002 DESIGN username. SENDING Backend transactions on node NodeA in group "username" at Mon Aug 28 15:06:43 2000: 63b01d10,0,0,0,0,2e59,43ea2002 DESIGN username. SENDING

RTR> RTR_RECEIVE_MESSAGE/TIME=0/CHAN=C

[The following lines arrive at the client from RTR after the user enters commands at the server.]

%RTR-S-OK, normal successful completion

channel name: C

msgsb

msgtype: rtr_mt_reply msglen: 25 usrhdl: 0 tid: 63b01d10,0,0,0,0,2e59,43ea2002

message

offset bytes text 000000 41 6E 64 20 74 68 69 73 20 69 73 20 6D 79 20 72 And this is my r 000010 65 73 70 6F 6E 73 65 2E 00 esponse..

RTR> RTR_ACCEPT_TX/CHANNEL=C %RTR-S-OK, normal successful completion

RTR> show transaction Frontend transactions on node NodeA in group "username" at Mon Aug 28 15:17:45 2000 Tid Facility FE-User State 63b01d10,0,0,0,0,2e59,43ea2002 DESIGN username. VOTING Router transactions on node NodeA in group "username" at Mon Aug 28 15:17:45 2000: 63b01d10,0,0,0,0,2e59,43ea2002 DESIGN username. VOTING Backend transactions on node NodeA in group "username" at Mon Aug 28 15:17:45 2000: 63b01d10,0,0,0,0,2e59,43ea2002 DESIGN username. COMMIT

4–6 RTR Interfaces

RTR> RTR_RECEIVE_MESSAGE %RTR-S-OK, normal successful completion

channel name: S

. . . msgtype: rtr_mt_accepted . . .

RTR> STOP RTR

RTR Management Station

Browser Interface

With the RTR browser interface, your management station has a network-browser-like display from which you can view RTR status and issue RTR certain commands with a point-and-click operation, rather than by entering commands. Figure 4–1 shows one screen of the browser interface as you may view it from your management station running Microsoft Internet Explorer. Not all RTR CLI commands are accessible to the browser interface, only the most commonly used commands are available with the RTR browser. The browser interface provides help (for forms input) and logging windows, and navigational aids between displays.

Application Programming Interfaces

You write application programs and management applications with the RTR application programming interfaces.

RTR Object-Oriented Programming Interface

You can use the object-oriented programming interface to write C++ applications that use RTR. For more information on the object-oriented programming interface, see the RTR C++

Foundation Classes manual and the RTR Application Design Guide.

RTR Interfaces 4–7

Application Programming Interfaces

Figure 4–1 RTR Browser Interface

Sample C++ client code

Example of object creation in an RTR client program.

// // Create a Transaction Controller to receive incoming messages // and events from a client. // RTRClientTransactionController *pTransaction = new RTRClientTransactionController(); // // Create an RTRData object to hold an ASCII message for the server. // RTRData *pMessage1 = new RTRData("You are pretty easy to use!!!"); // // Send the Server a message // sStatus = pTransaction->SendApplicationMessage(pMessage1); ASSERT(RTR_STS_OK == sStatus); // // Since we have successfully finished our work, tell RTR we accept the // transaction. // pTransaction->AcceptTransaction();

4–8 RTR Interfaces

Application Programming Interfaces

Sample C++ server code

void CombinationOrderProcessor::StartProcessingOrdersAtoL() { // // Create an RTRKeySegment for all ASCII values between "A" and "L." // m_pkeyRange = new RTRKeySegment (rtr_keyseg_string, //To process strings.

StartProcessingOrders(PARTITION_NAMEAToL,m_pKeyRange); }

// // Create an RTRData Oobject to hold each incoming message or event. This // object will be reused. // RTRData *pDataReceived= new RTRData(); // // Continually loop, receiving messages and dispatching them to the handlers. // while(true) {

sStatus = pTransaction->Receive(&pDataReceived); ASSERT(RTR_STS_OK == sStatus);

sStatus = pDataReceived->Dispatch(); ASSERT(RTR_STS_OK == sStatus);

}

Example of object creation in an RTR server program.

1, //Length of the key. OffsetIntoApplicationProtocol, //Offset value. "A", //Lowest ASCII value for partition. "L"); //Highest ASCII value for partition.

RTR C Programming Interface

You can use the C programming interface to write C applications that use RTR. For more information on the C programming interface, see the RTR C Application Programmer’s Reference Manual and the RTR Application Design Guide.

Snippets from client and server programs using the RTR Cprograming API follow and are more fully shown in the RTR Application Design Guide.

RTR Interfaces 4–9

Application Programming Interfaces

Sample C client code

Sample C server code

Example of an open channel call in an RTR client program:

status = rtr_open_channel(&Channel,

Flags, Facility, Recipient, RTR_NO_PEVTNUM, Access, RTR_NO_NUMSEG, RTR_NO_PKEYSEG);

if (Status != RTR_STS_OK)

Example of a receive message call in an RTR server program:

status = rtr_receive_message(&Channel,

RTR_NO_FLAGS, RTR_ANYCHAN, MsgBuffer, DataLen, RTR_NO_TIMOUTMS, &MsgStatusBlock);

if (status != RTR_STS_OK)

A client can have one or multiple channels, and a server can have one or multiple channels. A server can use concurrent servers, each with one channel. How you create your design depends on whether you have a single CPU or a multiple CPU machine, and on your overall design goals and implementation requirements.

4–10 RTR Interfaces

The RTR Environment

The RTR environment has two parts:

• The system management environment

• The runtime environment

The RTR System Management Environment

You manage your RTR environment from a management station, which can be on a node running RTR or on some other node. You can manage your RTR environment either from your management station running a network browser, or from the command line using the RTR CLI. From a managment station using a network browser, processes use the http protocol for communication.

The RTR system management environment contains four processes:

• The RTR Control Process, RTRACP

• The RTR Command Line Interface, RTR CLI

• The RTR Command Server Process, RTRCOMSERV

• The RTR daemon, RTRD

The RTR Control Process, RTRACP, is the master program. It resides on every node where RTR has been installed and is running. RTRACP performs the following functions:

• Manages network links

• Sends messages between nodes

The RTR Environment 5–1

The RTR System Management Environment

• Handles all transactions and recovery

RTRACP handles interprocess communication trafﬁc, network trafﬁc, and is the main repository of runtime information. ACP processes operate across all RTR roles and execute certain commands both locally and at remote nodes. These commands include:

• FACILITY

• SET LINK/NODE

• SET/CREATE PARTITION

• SHOW NODE

• STOP RTR

RTR CLI is the Command Line Interface that:

• Accepts commands entered locally by the system manager

• Sends commands to the Command Server Process RTRCOMSERV

• Can initiate commands on one node and execute them on another in most cases

5–2 The RTR Environment

Commands executed directly by the CLI include:

• DISPLAY

• DO (to the local operating system)

• MONITOR commands

• RECALL

• SET ENVIRONMENT

•SPAWN

• HELP

RTR COMSERV is the Command Server Process that:

• Receives commands from RTR

• Remains temporarily waiting for another command

• Exits automatically when idle for some time

The RTR System Management Environment

The Command Server Process executes commands both locally and across nodes. Commands that can be executed at the RTR COMSERV include:

• START RTR

• CREATE/MODIFY JOURNAL

• SHOW LINK/FACILITY/SERVER/CLIENT (ACP must be running)

• Application programmer commands (for testing and demonstration)

The RTR system management environment is illustrated in Figure 5–1.

Figure 5–1 RTR System Management Environment

RTRACP

RTR

COMSERV

RTR CLI

RTRD

Management Station Running Browser Software

RTRACP

RTR

COMSERV

RTRACP

RTRD

RTR

COMSERV

RTR CLI

LKG-11216-98WI

The RTR Environment 5–3

The RTR System Management Environment

Monitoring RTR

Transaction Management

RTR Monitor pictures or the RTR Monitor let you view the status and activities of RTR and your applications. A monitor picture is dynamic, its data periodically updated. RTR SHOW commands that also let you view status are snapshots, giving you a view at one moment in time. A full list of RTR Monitor pictures is available in the RTR System Manager’s Manual ‘‘RTR Monitoring’’ chapter and in the help ﬁle under RTR_Monitoring. Many RTR Monitor pictures are available using the RTR browser interface.

The RTR transaction is the heart of an RTR application, and transaction state characterizes the current condition of a transaction. As a transaction passes from one state to another, it undergoes a state transition. Transaction states are maintained in memory, and some are stored in the RTR journal for use in recovery.

RTR uses three transaction states to track transaction status:

• transaction runtime state

• transaction journal state

• transaction server state

Transaction runtime state describes how a transaction progresses from the point of view of RTR roles (FE, TR, BE). A transaction, for example, can be in one state as seen from the frontend, and in another as seen from the router.

5–4 The RTR Environment

Transaction journal state describes how a transaction progresses from the point of view of the RTR journal. The transaction journal state, not seen by frontends and routers, managed by the backend, is used by RTR for recovery replay of a transaction after a failure.

Transaction server state, also managed by the backend, describes how a transaction progresses from the point of view of the server. RTR uses this state to determine if a server is available to process a new transaction, or if a server has voted on a particular transaction.

The RTR SHOW TRANSACTION command shows transaction status, and the RTR SET TRANSACTION command can be used, under certain well-constrained circumstances, to change the state of a live transaction. For more details on use of SHOW and SET commands, see the RTR System Manager’s Manual.

The RTR System Management Environment

Partition Management

Partitions are subdivisions of a routing key range of values used with a partitioned data model and RTR data-content routing. Partitions exist for each range of values in the routing key for which a server is available to process transactions. Redundant instances of partitions can be started in a distributed network, to which RTR automatically manages the state and ﬂow of transactions. Partitions and their characterisitcs can be deﬁned by the system manager or operator, as well as within application programs.

RTR management functions enable the operation to manage many partition-based attributes and functions including:

• Creation/deletion of a partition with a user-speciﬁed name

• Deﬁning/changing a key-range deﬁnition

• Selecting a preferred primary node

• Selecting failover precedence between local and cross-site shadows

• Suspending/resuming operations to synchronize database backup with transaction ﬂow

• Overriding the automatic recovery procedures of RTR with manual recovery procedures, for added ﬂexibility

• Specifying retry limits for problem transactions

The operator can selectively inspect transactions, modify states, or remove transactions from the journal or the running RTR system. This allows for greater operational control and enhanced management of a system where RTR is running.

For more details on managing partitions and their use in applications, see the RTR System Manager’s Manual chapter ‘‘Partition Management.’’

The RTR Runtime Environment

When all RTR and application components are running, the RTR runtime environment contains:

• Client application

The RTR Environment 5–5

The RTR Runtime Environment

• Server application

• RTR shareable image, LIBRTR

• RTR control process, RTRACP

• RTR daemon, RTRD

Figure 5–2 shows these components and their placement on frontend, router, and backend nodes. The frontend, router, and backend can be on the same or different nodes. If these are all on the same node, there is only one RTRACP process.

Figure 5–2 RTR Runtime Environment

LIBRTR/RTRDLL LIBRTR/RTRDLL

Client

Application

RTRACP

RTRD

RTR

COMSERV

RTR CLI

Optional External Applet Not Running RTR

RTRACP

RTRD

RTR

COMSERV

LIBRTR/RTRDLL

Server

Application

RTRACP

RTRD

RTR

COMSERV

RTR CLI

LKG-11215-98WI

5–6 The RTR Environment

What’s Next?

This concludes the material on RTR concepts and capabilities that all users and implementors should know. For more information, proceed as follows:

If you are: Read these documents:

a system manager, system administrator, or software installer

an applications or system management developer, programmer, or software engineer

1. RTR Release Notes

2. RTR Installation Guide

3. RTR Migration Guide (if upgrading from RTR V2 to V3)

4. RTR System Manager’s

Manual

RTR Application Design Guide RTR C++ Foundation Classes RTR C Application

Programmer’s Reference Manual

The RTR Environment 5–7

Glossary

A few additional terms are deﬁned in the Glossary to the Reliable Transaction Router Application Design Guide.

ACID

Transaction properties supported by RTR: atomicity, consistency, isolation, durability.

ACP

The RTR Application Control Process.

API

Application Programming Interface.

applet

A small application designed for running on a browser.

application

User-written software that uses employs RTR.

application classes

The C++ API classes used for implementing client and server applications.

backend

BE, the physical node in an RTR facility where the server application runs.

bank

An establishment for the custody of money, which it pays out on a customer’s request.

Glossary–1

branch

A subdivision of a bank; perhaps in another town.

broadcast

A nontransactional message.

callout server

A server process used for transactional authentication.

channel

A logical port opened by an application with an identiﬁer to exchange messages with RTR.

client

A client is always a client application, one that initiates and demarcates a piece of work. In the context of RTR, a client must run on a node deﬁned to have the frontend role. Clients typically deal with presentation services, handling forms input, screens, and so on. A browser, perhaps running an applet, could connect to a web application that acts as an RTR client, sending data to a server through RTR.

In other contexts, a client can be a physical system, but in the context of RTR and in this document, such a system is always called a frontend or a node.

Glossary–2

client classes

C++ foundation classes used for implementing client applications.

commit process

The transactional process by which a transaction is prepared, accepted, committed, and hardened in the database.

commit sequence number (CSN)

A sequence number assigned to an RTR commit group, established by the vote window, the time interval during which transaction response is returned from the backend to the router. All transactions in the commit group have the same CSN and lock the database.

common classes

C++ foundation classes that can be used in both client and server applications.

concurrent server

A server process identical to other server processes running on the same node.

CPU

Central processing unit.

data marshalling

The capability of using systems of different architectures (big endian, little endian) within one application.

data object

See RTRData object.

deadlock

Deadly embrace, a situation that occurs when two transactions or parts of transactions conﬂict with each other, which could violate the consistency ACID property when committing them to the database.

disk shadowing

A process by which identical data are written to multiple disks to increase data availability in the event of a disk failure. Used in a cluster environment to replicate entire disks or disk volumes. See also transactional shadowing.

dispatch

A method in the C++ API RTRData class which, when called, interprets the contents on the RTRData object and calls an appropriate handler to process the data. The handler chosen to process the data is the handler registered with the transaction controller. This method is used with the event-driven receive model.

DTC

Microsoft Distributed Transaction Coordinator.

Glossary–3

endian

The byte-ordering of multibyte values. Big endian: high-order byte at starting address; little endian: low-order byte at starting address.

event

RTR or application-generated information about an application or RTR.

event driven

A processing model in which the application receives messages and events by registering handlers with the transaction controller. These handlers are derived from the C++ foundation class message and event-handler classes.

event handler

A C++ API-derived object used in event-driven processing that processes events.

facility

The mapping between nodes and roles used by RTR and established when the facility is created.

facility manager

A C++ API management class that creates and deletes facilities.

Glossary–4

facility member

A deﬁned entity within a facility. A facility member is a role and node combined. Can be a client, router or server.

failover

The ability to continue operation on a second system when the ﬁrst has failed or become disconnected.

failure tolerant

Software that enables an application to continue when failures such as node or site outages occur. Failover is automatic.

fault tolerant

Hardware built with redundant components to ensure that processing survives component failure.

frontend

FE, the physical node in an RTR facility where the client application runs.

FTP

File transfer protocol.

inquorate

Nodes/roles that cannot participate in a facility’s transactions are inquorate.

journal

A ﬁle containing transactional messages used for recovery.

key range

An attribute of a key segment, for example a range A to E or F to K.

key segment

An attribute of a partition that deﬁnes the type and range of values that the partition handles.

LAN

Local area network.

link

A communications path between two nodes in a network.

local node

The node on which a C++ API client or server application runs. The local node is the computer on which this instance of the RTR application is executing.

management classes

C++ API classes used by new or existing applications to manage RTR.

member

See facility member.

Glossary–5

message

A logical grouping of information transmitted between software components, typically over network links.

message handler

A C++ API-derived object used in event-driven processing that processes messages.

multichannel

An application that uses more than one channel. A server is usually multichannel.

multithreaded

An application that uses more than one thread of execution in a single process.

MS DTC

Microsoft DTC; see DTC.

node

A physical system.

nontransactional message

A message containing data that does not contain any part of a transaction such as a broadcast or diagnostic message. See transactional message.

Glossary–6

partition

RTR transactions can be sent to a speciﬁc database segment or partition. This is data content routing and handled by RTR when so programmed in the application and speciﬁed by the system administrator. A partition can be in one of three states: primary, standby, and shadow.

partition properties

Information about the attributes of a partition.

polling

A processing method where the application polls for incoming messages.

primary

The state of the partition servicing the original data store or database. A primary has a secondary or shadow counterpart.

process

The basic software entity, including address space, scheduled by system software, that provides the context in which an image executes.

properties

Application, transaction and system information.

property classes

Classes used for obtaining information about facilities, partitions, and transactions.

quorate

Nodes/roles in a facility that has quorum are quorate.

quorum

The minimum number of routers and backends in a facility, usually a majority, who must be active and connected for the valid completion of processing.

quorum node

A node, deﬁned speciﬁed in a facility as a router, whose purpose is not to process transactions but to ensure that quorum negotiations are possible.

quorum threshold

The minimum number of routers and backends in a facility required to achieve quorum.

roles

Roles are deﬁned for each node in an RTR conﬁguration based on the requirements of a speciﬁc facility. Roles are frontend, router, or backend.

Glossary–7

rollback

When a transaction has been committed on the primary database but cannot be committed on its shadow, the committed transaction must be removed or rolled back to restore the database to its pre-transaction state.

router

The RTR role that manages trafﬁc between RTR clients and servers.

RTR conﬁguration

The set of nodes, disk drives, and connections between them used by RTR.

RTR environment

The RTR run-time and system management areas.

RTRData object

An instance of the C++ API RTRData class. This object contains either a message or an event. It is used for both sending and receiving data between client and server applications.

secondary

See shadow.

Glossary–8

server

A server is always a server application or process, one that reacts to a client application’s units of work and carries them through to completion. This may involve updating persistent storage such as a database ﬁle, toggling the switch on a device, or performing another pre-deﬁned task. In the context of RTR, a server must run on a node deﬁned to have the backend role.

In other contexts, a server may be a physical node, but in RTR and in this document, physical servers are called backends or nodes.

server classes

C++ foundation classes used for implementing server applications.

shadow

The state of the server process that services a copy of the data store or primary database. In the context of RTR, the shadow method is transactional shadowing, not disk shadowing. Its counterpart is primary.

SMP

Symmetric MultiProcessing.

standby

The state of the partition that can take over if the process for which it is on standby is unavailable. It is held in reserve, ready for use.

TPS

Transactions per second.

transaction

An operation performed on a database, typically causing an update to the database. Analogous in many cases to a business transaction such as executing a stock trade or purchasing an item in a store. A business transaction may consist of one or more than one RTR transaction. A transaction is classiﬁed as original, replay, or recovery, depending on how it arrives at the backend:

Original—Transaction arrived on the ﬁrst attempt from the client. Replay—Transaction arrived after some failure as the result of a re-send from the client (that is, from the client transaction-replay buffers in the RTRACP). Recovery—Transaction arrived as the result of a backendto-backend recovery operation (recovery from the journal).

transaction controller

A transaction controller processes transactions. A transaction controller may have 0 or 1 transactions active at any moment in time. It is through the transaction controller that messages and events are sent and received.

Glossary–9

transactional message

A message containing transactional data.

transactional shadowing

A process by which identical transactional data are written to separate disks often at separate sites to increase data availability in the event of site failure. See also disk shadowing.

two-phase commit

A database commit/rollback concept that works in two steps: 1. The coordinator asks each local recovery manager if it is able to commit the transaction. 2. If and only if all local recovery managers agree that they can commit the transaction, the coordinator commits the transaction. If one or more recovery managers cannot commit the transaction, then all are told to roll back the transaction. Two- phase commit is an all-or-nothing process: either all of a transaction is committed, or none of it is.

WAN

Wide area network.

Glossary–10

ACID, 2–4 Anonymous client, 1–22 API, 4–1 Application

distributed, 2–4 software, 2–2

Authentication, 1–20

Backend, 2–1

loss, 3–3 BE, 2–1 Broadcast, 2–3

Index

DECnet, 1–23 Distributed applications, 2–4 DTP standard, 2–10

Facility, 2–3 Failure tolerance, 3–2 Fault tolerance, 3–2 FE, 2–1 Firewall tunneling software, 1–22 Frontend, 2–1

CPU loss, 3–3

Key range, 1–16

Callout

server, 1–20, 3–1 Client

anonymous, 1–22

processes, 2–1 Concurrent server, 3–1

Database, 2–1, 2–2

locks, 2–5

shared, 2–5 Data model

partitioned, 2–5

LAN, 1–23 Link failure recovery, 3–2 Load balance, 1–17 Lock

database, 2–5

Microsoft SQL Server, 2–10

Index–1

Network

wide area, 1–18 Nodes, 2–2

Object-oriented, 2–5 Oracle

RDBMS, 2–10

Parallel execution, 2–4 Partitioned data model, 2–5 Processes

client, 2–1

server, 2–1

RDBMS, 2–10 Recovery, 3–2 Reliability features, 3–1 Resource manager, 2–10 RM, 2–10 Router, 2–1

failover, 3–2

layer, 2–2

loss, 3–3 RTR

API, 4–1

broadcasts, 2–3

facilities, 2–3

ﬂexibility and growth, 2–3

reliability features, 3–1

Server (cont’d)

shadow, 3–1 spare, 1–16 standby, 3–1 types, 3–1

Shadow

server, 1–17, 3–1 Shared database, 2–5 Spare server, 1–16 SQL

server, 2–10 Standby

server, 3–1 Subscribe, 2–3

TCP/IP, 1–23 Three-layer model, 2–1 TM, 2–10 TR, 2–1 Transaction, 2–4

integrity, 2–4

replay, 3–2 Transaction manager, 2–10 Tunnel, 1–22 Two-phase commit, 3–2

WAN, 1–23 Wide area network, 1–18

X/Open DTP, 2–10 XA

interface, 2–10

Security

check, 1–20

Server

callout, 3–1 concurrent, 3–1

Index–2

Compaq Reliable Transaction Router User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual