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

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100 CICS for AIX as the Transaction Server Planning Guide, S20H-4758, and DB2 for AIX Installation and Operation Guide, S20H-4757, for more details. Number of XAD Entries: You can create multiple databases running under one instance of the DB2 for AIX database manager. For each database, CICS for AIX requires an XAD entry with the name of the database as the connection string (XA open string). So, there should be as many XAD entries as there are databases being accessed by the application. A CICS application can switch from one database to another explicitly, using the SQL CONNECT command. If you do not explicitly connect to a database in your application, CICS for AIX assumes that the database the application wants to access is the one that was last successfully connected to. It may be possible to physically merge multiple databases into a single database, in which case the run-time overhead of database switching in your CICS applications can be saved. Whether this is practical or not will require detailed knowledge about the usage profiles of the databases used by your CICS applications. The backup and recovery requirements within DB2 for AIX or business requirements may be overriding obstacles against such a merge, however. Number of Database Accesses: There is typically a noticeable overhead for crossing between a CICS for AIX application program and a relational database, so the number of such crossings should be minimized for performance reasons. The use of static SQL or SQL stored procedures can assist in reducing the overhead due to crossing between the CICS application program and the relational database. Security Implications: It is important to understand the security implications when accessing relational database resources from CICS in an XA-enabled environment. The granularity of relational database access from CICS in this type of environment is at the region level. All transactions that run against an XA-enabled database access that database with the same database userid, that of the CICS for AIX region. This is an implication of the XA architecture under which resource manager authentication occurs. For CICS, the xa_open call is issued during application server initialization. At this point, a connection is established to the relational database with a specific database userid. Each transaction that runs on this particular application server inherits the established database connection and, by implication, the established database authorization. Each CICS application server in a particular region connects to the database with the same database userid (because it uses the same xa_open() string). Therefore, each and every transaction that makes EXEC SQL calls makes them under the authority of this specific database userid. There is no mechanism for CICS to provide DB2 for AIX with the actual userid that invokes the CICS transactions. A security policy in an XA-enabled CICS environment should therefore be based on CICS security facilities. CICS has facilities to control user access to the system as well as to specific resources, such as the transactions. You should consider implementing CICS transaction security and CICS resource security to limit access to those transactions.
DB2 has the concept of binding a program (or package) to a database. For CICS transactions that use static SQL statements, the binder′s privileges are used to access the database. Because all transactions execute under the same database userid, this userid must still be granted EXECUTE privileges against packages that involve CICS transactions. CICS transactions that use dynamic SQL have their access authentication done at run time. For more information about DB2 security in an XA environment, see the DATABASE 2 for AIX Administration Guide, S20H-4580. The local configuration is probably the easiest to implement, but the worst from a resource distribution point of view. For best throughput the database machine should be located on a dedicated machine. With a local configuration, the database server and CICS for AIX region compete for system resources such as processor cycles and memory. 7.4.1.2 Remote Configuration In a remote configuration the CICS for AIX region and the DB2 for AIX server reside in two separate RISC System/6000 machines. IBM DB2 Server for AIX must be installed on the remote database machine, and an instance of a DB2 for AIX server must be created there as well. In the local machine where the CICS for AIX region resides, DB2 Client for AIX must be configured. The Client Application Enabler for AIX (CAE) product provides the DB2 client code. CAE is a run-time environment for applications accessing a remote database server. To connect a DB2 Client for AIX to a DB2 Server for AIX you use the remote data services (RDS) protocol, also known as DB2 common server private protocol. RDS supports distributed unit of work (DUW) with two-phase commit protocol. A shared object, an XAD entry, and the switch load file are required on the local (CICS for AIX region) machine. The DB2INSTANCE environment variable must be set to the DB2 instance name and be present on both the local and the remote machines. When the CICS application server (cicsas) issues the xa_open call to the local DB2 client, the database alias is obtained from the XA open string, and the DB2INSTANCE value is obtained from the CICS for AIX region environment file. Then the system database directory, for that DB2INSTANCE checked for a match in the database alias name. From the matched entry in the system database directory, the machine name is obtained and is checked against the machine names in the node directory. Once a match is found, the port number and the host name are obtained and checked against the /etc/services file of the host name for a port number match. If the port numbers match, a connection is established to the DB2 for AIX server on the host name system, which is the remote machine. Figure 30 on page 102 shows a CICS for AIX region accessing databases in a remote DB2 system. Chapter 7. Interactions with the DB2 Family of Products 101
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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
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3.4.6 Intersystem Communication CIC
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3.4.8 Data Location 44 CICS for AIX
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3.4.11 Operations plan to cope with
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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 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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Page 96 and 97: 6.1.2 Encina Toolkit Server Core 6.
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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 126 and 127: 7.5 Summary 108 CICS for AIX as the
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
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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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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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