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DB2 group attach facility

You can now use the group attach facility of DB2® with CICS®. Instead of a specific DB2 subsystem, you can specify a DB2 group ID on the DB2CONN resource definition. With a DB2GROUPID specified, the group attach facility chooses any member of the group that is active on the local MVS™ image for the connection to CICS (members that are active on other MVS images are not eligible for selection).

Specifying DB2 IDs

There are some restrictions regarding the use of the DB2ID and DB2GROUPID attributes:

If an installed DB2CONN definition specifies a DB2ID, and you want to override this and switch to the group attach facility:

If an installed DB2CONN definition specifies a DB2GROUPID, and you want to override this and switch off the group attach facility, you can:

The INITPARM system initialization parameter method of specifying a DB2ID (INITPARM=(DFHD2INI=db2id)) continues to be supported, but is effective only if both the DB2GROUPID and DB2ID attributes are blank in the DB2CONN resource definition. If a DB2CONN specifies a DB2ID or a DB2GROUPID, INITPARM is ignored.

Note that if you issue an INQUIRE DB2CONN command, or look at the statistics output, you might sometimes see both a DB2GROUPID and a DB2ID. This happens under the following circumstances:

Indoubt resolution of units of work (UOWs)

You need to consider the resolution of indoubt units of work when you are using the group attach facility. CICS maintains a history of the last DB2 data sharing group member to which it connected, which is cataloged and maintained across warm, emergency and cold starts (but not initial starts). During connection to DB2, the CICS DB2 attachment facility checks this history to see if any outstanding UOW information is being held for the last DB2 data sharing group member to which it connected. If no outstanding UOW information is being held, the group attach facility operates normally and can choose any active member of the data sharing group for the connection. However, if there are outstanding units-of-work involving a specific DB2 member, the connection process depends on the value specified for the new RESYNCMEMBER attribute of the DB2CONN resource definition. The new RESYNCMEMBER attribute on the DB2CONN resource definition gives you some control over a connection when there are outstanding UOWs, and operates as follows:

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