Addressing OLTP Solutions with CICS: The Transaction Server ... - Ibm

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3.2 Implementation 3.2.1 Components 28 CICS for AIX as the Transaction Server be read only once. Transient data is used for queued data such as an audit trail and output for a printer. Temporary storage queue names do not have to be previously defined, and they can be updated in place. Temporary storage queues can be written to a file or to memory. For a more detailed description and comparison of these queue services, see CICS on Open Systems Application Programming Guide, SC33-1568-01. • Relational database services CICS provides access to relational databases that provide a programmable interface through SQL commands in either COBOL, C, or PL/1. Provided that the relational database management system (RDBMS) is compliant with the X/Open XA interface, it is possible to use two-phase commit processing between the resources coordinated by CICS. See section Chapter 7, “Interactions with the DB2 Family of Products” on page 85 for more details about processing with DB2. • Journal services CICS provides facilities for creating and maintaining journals during CICS processing. A journal is a set of special-purpose sequential files. An application can use a journal as an audit trail to record which users submitted which transactions or which users accessed which records in a file, for example. In this section we provide an introduction to the structure of a CICS for AIX region. We do not provide a detailed explanation of the internals of CICS for AIX. A CICS for AIX region consists of: • A set of program executables, that is, the system code required for the product, including the necessary CICS, Encina, and DCE code • A file structure that contains definitions for the region, servers, clients, and a number of run-time files. The definitions are used to configure the system. The files holding each set of definitions are referred to as stanzas. The run-time files contain such items as the message log, warm-start definitions, and recovery log. • A set of application programs provided by the enterprise that will perform the required business processing • User data, which may be held in an Encina SFS, in a database, or on a remote system See the CICS for AIX Planning and Installation Guide, GC33-1773-00, for more information about the directory structure of the regions, servers, and clients. The major components of CICS for AIX are: • The CICS client processes that you use to attach to a region and through which you run transactions • The transaction scheduler, a process that receives requests to run transactions, prioritizes and schedules them, and then dispatches them to an application server for processing
• A pool of application servers that execute the transactions and interact with the CICS client processes to send and receive terminal input and output • The CICS queue and file manager, which is responsible for managing the CICS queues and application files • A PPC Gateway server used when required for communication across SNA networks 3.2.1.1 Client Processes A CICS user interacts with a CICS client. The client communicates with the CICS region processes. The client process does not have to be located in the same physical machine as the CICS region. The clients available and the protocols used are covered in Chapter 4, “Using CICS Clients” on page 49. 3.2.1.2 Transaction Scheduler The transaction scheduler (also known as the remote procedure call (RPC) listener) is a multithreaded process responsible for scheduling and dispatching transactions to be run. It is configured with the details of all users, devices, and transactions in the region. As these change, the scheduler is kept up to date. Each transaction has an associated priority. When a transaction is submitted, the transaction scheduler computes an overall priority which it uses to prioritize requests in times of heavy demand. An incoming RPC from a client is processed on one of the threads of the transaction scheduler. The default number of threads is ten times the maximum number of application servers that is specified in the Region Definition stanza, subject to the limit of the number of threads allowed per process by the operating system. The limit on the number of listener threads is approximately 500. The exact number varies according to the number of other threads that exist in the transaction scheduler. In most cases a transaction can be scheduled synchronously when fewer than 80% of the available concurrent RPC server threads have work to do. When the 80% threshold is exceeded, an asynchronous mode of scheduling is adopted. The processing that takes place in synchronous mode is as follows: If there is a free application server, the transaction scheduler signals the application server that there is work to be processed, and the transaction will run immediately. If there is no free application server or the transaction cannot be processed for some reason, such as a user-imposed limit on the number of transactions that may run concurrently, the transaction is placed on a work queue to wait for a free application server. In the asynchronous mode of operation, the RPC from the CICS client is returned with a notification that the transaction will be processed later. When a CICS application server becomes free, it processes the transaction and sends the response to the CICS client. The work queue is held within and managed by CICS. The number of keep alive RPCs between the transaction scheduler and the CICS client is reduced. A keep alive RPC occurs at 1-sec intervals and is required when there is an outstanding RPC, which there would be in this case between the client and the CICS region. Chapter 3. CICS for AIX 29
Page 1: Addressing OLTP Solutions with CICS
Page 4 and 5: Take Note! Before using this inform
Page 6 and 7: iv CICS for AIX as the Transaction
Page 8 and 9: 9.4 Security Issues on the Internet
Page 10 and 11: viii CICS for AIX as the Transactio
Page 12 and 13: x CICS for AIX as the Transaction S
Page 14 and 15: xii CICS for AIX as the Transaction
Page 16 and 17: The Team That Wrote This Redbook xi
Page 18 and 19: xvi CICS for AIX as the Transaction
Page 20 and 21: 2 CICS for AIX as the Transaction S
Page 22 and 23: 1.2 Complex OLTP Business Environme
Page 24 and 25: Figure 2. OLTP Complex for XYZ Insu
Page 26 and 27: By using common application program
Page 28 and 29: 1.5 OLTP Market 10 CICS for AIX as
Page 30 and 31: Figure 5. OLTP Market Segmentation
Page 32 and 33: 14 CICS for AIX as the Transaction
Page 34 and 35: 2.1 IBM Software Servers 2.1.1 Lotu
Page 36 and 37: 2.2.1 CICS Clients V1.1.0 A Transac
Page 38 and 39: 2.2.4 CICS Internet Gateway for AIX
Page 40 and 41: 3.1 Services CICS for AIX is a very
Page 42 and 43: 3.1.2 CICS API 24 CICS for AIX as t
Page 44 and 45: 3.1.3.1 Terminal Users and CICS Reg
Page 48 and 49: 3.2.2 Processes 3.2.1.3 Application
Page 50 and 51: 3.3.1 DCE RPC 3.3.2 TCP/IP 32 CICS
Page 52 and 53: Figure 9. Interconnection Using Enc
Page 54 and 55: connect to a PPC Gateway server mac
Page 56 and 57: Figure 12. Interconnection Using TC
Page 58 and 59: 3.4.3 Configuration 3.4.4 Managing
Page 60 and 61: 3.4.6 Intersystem Communication CIC
Page 62 and 63: 3.4.8 Data Location 44 CICS for AIX
Page 64 and 65: 3.4.11 Operations plan to cope with
Page 66 and 67: 3.5 Summary 48 CICS for AIX as the
Page 68 and 69: Figure 13. Application Server Model
Page 70 and 71: 4.2.1 CICS External Call Interface
Page 72 and 73: By means of mapping files, you can
Page 74 and 75: 4.3 Versions 56 CICS for AIX as the
Page 76 and 77: 4.4 Sample Network Configurations 4
Page 78 and 79: 4.5.1 CICS Client for OS/2 60 CICS
Page 80 and 81: 4.5.2 CICS Client for DOS 62 CICS f
Page 82 and 83: 4.5.5 CICS Client for AIX CICS Clie
Page 86 and 87: 4.6 Summary 68 CICS for AIX as the
Page 88 and 89: 5.1.1 DCE Threads 5.1.2 Remote Proc
Page 90 and 91: The GDS is based on the CCITT X.500
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6.1.2 Encina Toolkit Server Core 6.
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80 CICS for AIX as the Transaction
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is also necessary to use native AIX
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7.1 X/Open XA Interface 7.1.1 X/Ope
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Communication between the transacti
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7.2.2 Single-Phase and Two-Phase co
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Figure 28. Switching Access among D
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Figure 30. CICS Access to Remote DB
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emote DRDA database. Information ab
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As the COMMAREA has an allowable ma
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7.5 Summary 108 CICS for AIX as the
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8.2 Workload Management 112 CICS fo
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8.4.2 System Management Application
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Figure 36. The CICS SM GUI 8.4.6 Di
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Figure 37. CICS SM Component Distri
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Figure 38. Combining Resources 122
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8.5.2 The Reference System 124 CICS
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8.6 Planning Considerations for CIC
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9.1 Some Terminology 9.2 Services 1
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Figure 41. CICS Internet Gateway fo
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9.3.3 Data Integrity The Web was or
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9.3.5 High Availability The drawbac
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or employee records, eavesdropping
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• Type, size, and quantity of rec
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10.3.3 Writing ECI and EPI Applicat
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The ANIMATOR debugging tool enables
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10.8 Summary 154 CICS for AIX as th
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11.1 The Big Picture 158 CICS for A
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11.2 User Access 160 CICS for AIX a
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Figure 44. Access to Various DB2 Da
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takes place over TCP/IP or SNA comm
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provide greater protection in the u
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How Customers Can Get ITSO Redbooks
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design. The process of composing a
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A year later ISC gave SQL formal in
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designing efficient applications 15
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