IMS catalog secondary index

Overview

The IMS application environment can contain an arbitrary number of databases that are each accessed through one or many IMS PSBs. Before an IMS database can be safely changed or removed, the database administrator must know which applications have a dependency on the database. The IMS catalog secondary index provides a fast processing path for determining which PSBs have a dependency on a specific DBD.

The IMS catalog secondary index (DFSCX000) root segment type, DBDPSB, is logically linked to the DBDXREF segment type in the IMS catalog database. The DFSC prefix is replaced with the catalog alias prefix, if one is defined to IMS.

The IMSNAME field of the DBDXREF segment type is indexed as the DBD2PSB XDFLD for the secondary index relationship. The IMSNAME field contains the 8-character IMS name for the DBD that is referenced by the PSB described by the catalog record. You can search the DBDXREF segment on the IMSNAME (the DBD name), PSBNAME, or TSVERS fields.

Usage

You can use the IMS catalog secondary index to process the IMS catalog metadata in the following ways:

• Use the DFSCATSX PCB to process the primary catalog database (DFSCD000) with PROCSEQ=DFSCX000. The DBDXREF segment type is the only segment type defined as a sensitive segment in this PCB.
• Use the DFSCATX0 PCB to directly process the catalog secondary index. The secondary index root segment type (DBDPSB) is the only segment type in the secondary index.

Both PCBs are included in the IMS catalog PSBs, DFSCPxxx, that are dynamically attached to user PSBs when the IMS catalog is active.