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

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92 CICS for AIX as the Transaction Server database will be accessed as a non-XA database even though the RDBMS may be XA capable. Figure 27 shows the relationship between CICS and a resource manager for both an XA- and a non-XA-enabled database. In the case of the XA-enabled database, transactional information is exchanged between CICS and the resource manager. There is no such exchange for the non-XA-enabled database. Figure 27. XA-Enabled and Non-XA-Enabled Relational Databases If an XA-enabled database connection has been defined in a CICS for AIX region, that connection will always be used. It is not possible to deactivate the use of the XA interface once the region has started. If you want to use a non-XA definition, the entry must be removed from the XAD stanza file, and the CICS for AIX region must be restarted. Simultaneous access to an XA-enabled database and a non-XA-enabled database from a CICS for AIX region is not supported, that is, only databases defined in the XAD entry for a CICS region can be accessed by a transaction running within that region. You can use a non-XA connection to the second database concurrently with an XA connection to the first database, that is, one-phase and two-phase supporting databases can be accessed concurrently within a transaction, but the one-phase supporting database is restricted to read-only access. CICS establishes implicit connection to the first database through the XA interface according to the XAD entry during CICS startup time. To connect to the second database, you have to connect explicitly by using an EXEC SQL CONNECT call. To reconnect to the first database, you have to connect to it explicitly by using an EXEC SQL CONNECT call even though the first database is defined in the XAD entry. Table 5 on page 93 compares an XA-enabled relational database and a non-XA-enabled relational database. The resource manager is DB2 for AIX.
Table 5. XA-enabled and Non-XA-Enabled Relational Databases XA-Enabled Relational Database Transactional information exchange between CICS for AIX and DB2 for AIX takes place. Coordinated commitment or rollback of both CICS resources and RDBMS table changes occurs through the EXEC CICS SYNCPOINT call. An XAD entry (Product Definition) is required for each database. CICS for AIX has to be cold started after any changes to the XAD stanza file or the addition of new XAD stanza file entries. Provides better performance because CICS transactions can reuse an XA-managed database connection while the application server (cicsas) is running, without having to call EXEC SQL CONNECT repeatedly. CICS immediately abends the region if it cannot open a connection to the database. CICS facilities for transactional control must be used. These are the EXEC CICS SYNCPOINT and EXEC CICS SYNCPOINT ROLLBACK commands. CICS SYNCPOINT processing takes longer than an SQL COMMIT call because it includes coordination of syncpoint among all resources managers involved. CICS application programs must be compiled with the NOSQLINIT option. Database connection stays with the application server (cicsas). Hence it is conveyed across an EXEC CICS LINK or EXEC CICS XCTL call. Database connection is established according to the XAD definitions at CICS startup time. There is no need for the CICS transaction to make the database connection. Non-XA-Enabled Relational Database Transactional information exchange between CICS for AIX and DB2 for AIX does not take place. CICS application has to issue EXEC SQL COMMIT call or EXEC SQL ROLLBACK call explicitly for the changes of RDBMS tables. Only the CICS resource changes are affected by the EXEC CICS SYNCPOINT call. An XAD entry is not required. A CICS application that wants to connect to a particular database has to issue an EXEC SQL CONNECT call. CICS applications have to issue the EXEC SQL CONNECT call to start the database connection for each transaction. Hence there is a greater overhead. CICS region keeps running when the EXEC SQL CONNECT call issued by a CICS application fails. RDBMS facilities must be used. They are the EXEC SQL COMMIT, EXEC SQL ROLLBACK, and EXEC SQL SYNCPOINT commands. SQL COMMIT processing is faster, but it only works if no other resource managers are involved in the transaction. Furthermore, using SQL COMMIT in a transaction prevents you from issuing an EXEC CICS SYNCPOINT call in the same transaction. Special compile options are not required. Database connection cannot be conveyed across the EXEC CICS LINK or EXEC CICS XCTL call. You must disconnect from the database before these calls and reconnect in the called program. CICS transaction has to connect to the database through an EXEC SQL CONNECT call before making any SQL access calls. Chapter 7. Interactions with the DB2 Family of Products 93
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Addressing OLTP Solutions with CICS
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Take Note! Before using this inform
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iv CICS for AIX as the Transaction
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9.4 Security Issues on the Internet
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viii CICS for AIX as the Transactio
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x CICS for AIX as the Transaction S
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xii CICS for AIX as the Transaction
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The Team That Wrote This Redbook xi
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xvi CICS for AIX as the Transaction
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2 CICS for AIX as the Transaction S
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1.2 Complex OLTP Business Environme
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Figure 2. OLTP Complex for XYZ Insu
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By using common application program
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1.5 OLTP Market 10 CICS for AIX as
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Figure 5. OLTP Market Segmentation
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14 CICS for AIX as the Transaction
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2.1 IBM Software Servers 2.1.1 Lotu
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2.2.1 CICS Clients V1.1.0 A Transac
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2.2.4 CICS Internet Gateway for AIX
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3.1 Services CICS for AIX is a very
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3.1.2 CICS API 24 CICS for AIX as t
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3.1.3.1 Terminal Users and CICS Reg
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3.2 Implementation 3.2.1 Components
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3.2.2 Processes 3.2.1.3 Application
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3.3.1 DCE RPC 3.3.2 TCP/IP 32 CICS
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Figure 9. Interconnection Using Enc
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connect to a PPC Gateway server mac
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Figure 12. Interconnection Using TC
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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 84 and 85: 66 CICS for AIX as the Transaction
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
Page 92 and 93: egion or server it is looking for.
Page 96 and 97: 6.1.2 Encina Toolkit Server Core 6.
Page 100 and 101: is also necessary to use native AIX
Page 104 and 105: 7.1 X/Open XA Interface 7.1.1 X/Ope
Page 108 and 109: Communication between the transacti
Page 112 and 113: 7.2.2 Single-Phase and Two-Phase co
Page 116 and 117: Figure 28. Switching Access among D
Page 120 and 121: Figure 30. CICS Access to Remote DB
Page 122 and 123: emote DRDA database. Information ab
Page 124 and 125: As the COMMAREA has an allowable ma
Page 130 and 131: 8.2 Workload Management 112 CICS fo
Page 134 and 135: 8.4.2 System Management Application
Page 136 and 137: Figure 36. The CICS SM GUI 8.4.6 Di
Page 138 and 139: Figure 37. CICS SM Component Distri
Page 140 and 141: Figure 38. Combining Resources 122
Page 142 and 143: 8.5.2 The Reference System 124 CICS
Page 146 and 147: 8.6 Planning Considerations for CIC
Page 152 and 153: 9.1 Some Terminology 9.2 Services 1
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Page 156 and 157: 9.3.3 Data Integrity The Web was or
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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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