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

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3.2.2 Processes 3.2.1.3 Application Servers An application server is a multithreaded CICS process that provides a complete environment for running a CICS transaction. An application server obtains work in one of two ways: (1) the transaction scheduler signals that there are transactions to be processed, or (2) at the end of processing its current transaction it looks to see whether there is any outstanding work on the work queue. If a transaction is conversational, it is processed by one application server, which is used by the transaction for the life of the transaction. Thus, if a transaction were waiting for terminal input and the user went for coffee, it would hold the application server, then the application server, making it unavailable to process other work. Conversational programming is not a good programming model to use. See 3.4.5, “Application Design” on page 41. If the transaction is pseudo conversational, each transaction in turn can be processed on a different application server. When you configure CICS, you specify the minimum and maximum number of application servers for the region. The application manager always ensures that the minimum number is present. Application servers can be created and destroyed up to the maximum number defined, depending on the workload of the CICS system. All application servers have to be allocated on the same machine. The machine does not have to be the same machine as the client process, however. Application servers communicate with each other through signals and shared memory and use RPCs to communicate with other components of the system. 3.2.1.4 CICS Queue and File Management CICS queue and file management is the function within CICS that manages the physical files, auxiliary temporary storage queues, intrapartition transient data queues, and locally managed, queued, automatic initiation requests. With the introduction of CICS for AIX V2.1, it is now possible to use a DB2 Version 2 database instead of an Encina SFS for queue and file management. The same API is used for both the Encina SFS and DB2 cases. 3.2.1.5 PPC Gateway Server A CICS for AIX region can use one or more PPC Gateway servers to access SNA hosts. As with Encina SFS, an application server becomes a client of the PPC Gateway. In this section we take a look at the actual CICS processes under AIX. Table 2 lists the CICS processes and briefly describes their functions. Table 2 (Page 1 of 2). CICS for AIX Process Names and Functions Component Name Function cics Main The first process invoked cicsas Application server 30 CICS for AIX as the Transaction Server The process on which an application runs. Typically there are a number of these processes.
Table 2 (Page 2 of 2). CICS for AIX Process Names and Functions Component Name Function cicsam Application manager cicsic Interval control cicsip Client′s listener cicsld Log demon server cicsrl RPC listener cicsrm Recovery manager cicsrs Recovery server cicssl Local SNA listener 3.3 Intercommunication Creates the application servers and tidies up resources if an application server ends unexpectedly Handles requests to run asynchronous transactions as required Accepts CICS family TCP/IP connection requests from CICS on Open Systems clients and CICS regions Writes to the CICS log when signaled by an application server Picks up incoming RPCs that request a new transaction to start processing. The request is placed on a work queue from which the application servers read. Initializes recovery as required. Creates recovery processes to recover transactions Recovers an interrupted transaction or a crashed application server Accepts intersystem communication requests from local SNA services The use of multithreading enables multiple concurrent units of work to be active within a single operating system process, providing concurrence within applications. The multiple processes and multithreading of the CICS for AIX architecture lend themselves to the exploitation of RISC System/6000 SMP hardware. In this section we examine the protocols on which the CICS intercommunication facilities are implemented. Knowing which protocols are available will be helpful in planning for a new service or establishing new communication paths between existing services. A CICS for AIX region may well want to communicate with any or all of the following: • Other CICS on Open Systems systems Chapter 3. CICS for AIX 31
Page 1: Addressing OLTP Solutions with CICS
Page 4 and 5: Take Note! Before using this inform
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Page 8 and 9: 9.4 Security Issues on the Internet
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Page 16 and 17: The Team That Wrote This Redbook xi
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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
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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
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Page 42 and 43: 3.1.2 CICS API 24 CICS for AIX as t
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Page 46 and 47: 3.2 Implementation 3.2.1 Components
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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
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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
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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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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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