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The Extender for Db2 is situated between your application (such as QMF) and the local Db2 subsystem (and the server). By providing a Db2 interface to the application, all requests from the application are intercepted by the Extender for Db2 before reaching either the local Db2 subsystem, or the server. The Extender for Db2 uses either one of two standard Db2 Attachment Facilities as the Db2 interface to your application:
Before installing the Extender for Db2, you must determine which facility is used by your application and is suitable for your application environment. For more information about the advantages and disadvantages of each facility, see the IBM Db2 Application Programming and SQL Guide.
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If your application uses the Db2 Call Attach Facility (CAF), there are two ways to access the CAF language interface:
The advantages and limitations of using either CAF access mode are fully explained in the IBM Db2 Application Programming and SQL Guide. The Extender for Db2 supports both modes of CAF access to Db2. Depending upon whether your application uses CAF explicit loading or CAF link-editing of DSNALI, you can install the Extender for Db2 to support either mode of CAF access to Db2.
You can use the explicit loading feature of Db2 with the Extender for Db2. For the Extender, simply allocate the qualif.HOMEEXT.LOAD library before the standard Db2 load libraries.
The modules in qualif.HOMEEXT.LOAD must be invoked before the modules in the standard Db2 load library, DSNxxx.DSNLOAD because the library qualif.HOMEEXT.LOAD contains the entry points DSNALI, DSNHLI, and DSNTIAR, which have similar names to the standard Db2 entry points. If the library qualif.HOMEEXT.LOAD is placed before the standard Db2 load library in your JCL or CLIST, the Extender for Db2 module is invoked before the identical modules in the Db2 standard library.
Your application product allocations (such as those for QMF) are usually placed in sequence order between the Extender for Db2 libraries and the standard Db2 load library. For example, QMF requires ISPF load libraries. These are allocated between the Extender for Db2 libraries and the Db2 load library. For more information about the specific Extender for Db2 installation steps, see Installation Procedure.
To allocate the Extender for Db2 libraries for run-time, place the library qualif.HOMEEXT.LOAD the application-specific load libraries, and the standard Db2 load libraries, in that order (referred to as the server concatenation), in your load library search path. Most installations offer the following choices:
Note: If the chosen load library file allocation contains APF authorized data sets, the Extender for Db2 load data sets must also be APF authorized. If the Extender for Db2 load data sets are not APF authorized and are integrated with other APF authorized data sets under a ddname such as STEPLIB, the APF authorization of all the data sets is invalidated.
If your application link-edits DSNALI using the CAF interface to Db2, you must instead link-edit the Extender for Db2's DSNALI interceptor stub (located in qualif.HOMEEXT.LOAD) to your application. For more information about the specific Extender for Db2 installation steps, see Installation ProcedureInstallation Procedure.
The Extender for Db2 supports applications that communicate to Db2 via the DSN Command Processor Facility. As with the support for CAF link-edit with DSNALI, you can enable the Extender for Db2 to use the DSN Command Processor for your application. To do so, simply perform a link-editing step of the Extender for Db2's DSNELI with your application program. For more information about the specific Extender for Db2 installation steps, see Installation Procedure.
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