Switching from group-generic to member-specific access

To switch from group-generic to member-specific access, you must break the affinity between systems.

About this task

Member-specific access provides several benefits over group-generic access, including better workload balancing and two-phase commit support. However, before a requester that was using group-generic access can take advantage of these benefits by switching to member-specific access, you need to break any affinity that might exist between the requester and the server. This section describes how to break the affinity between systems.

If a requester uses group-generic access to connect to a data sharing group with two-phase commit support enabled on both subsystems, VTAM® records information in the coupling facility about which member of the group is involved in the communication. This information is required to ensure that future VTAM sessions are directed to the same group member, thus providing access to the correct member log for resolution of indoubt threads. When switching the requester from using group-generic access to member-specific access, you must break this affinity between the systems.

Procedure

To break the affinity between systems:

  1. Shut down the network connections between the requester and the data sharing group.
    Some ways to do this include:
    • Using the VTAM command VARY NET,INACT,ID=luname
    • Entering the Db2 command STOP DDF
  2. From an active member of the data sharing group, issue the RESET GENERICLU command.
    Issue this command from the member with the VTAM affinity to the requester whose information is being deleted.
    • If the requester is configured to pass its own, real LU name to the data sharing group, netid is the net ID of the requester, and luname is the real LU name of the requester.
    • If the requester is configured to pass its generic LU name, netid is the net ID of the requesting data sharing group, and luname is the generic LU name of the requesting data sharing group.
  3. Change the requester's CDB to ensure that the requester uses member-specific access from this point forward.
    • Populate the requester's SYSIBM.LULIST table.

      Make sure that the GENERIC column of the requester's SYSIBM.LUNAMES table contains a value of N for the row that is associated with the data sharing group.

    • Delete existing generic LU names from the SYSIBM.LUNAMES table.
  4. Re-enable the network connections between the requester and the data sharing group.

    Unlike group-generic access, which uses generic LU names, member-specific access uses real LU names. When switching the requester from using group-generic access to member-specific access, remember to delete existing generic LU names.