ACB library member online change

If an IMS system uses an ACB library in an IMSplex environment, you can use the ACB member online change (OLC) function to add or change individual members of the ACB library, or the entire ACB library, and bring these new or changed members online without quiescing the IMSplex or refreshing the active ACB library.

The ACB member online change function does not apply when the IMS management of ACBs is enabled. In this case, individual ACB members can be changed online by submitting the changes to IMS by using either DDL or one of the IMS catalog population utilities and, if the change is not activated in the online system automatically, issuing the IMPORT DEFN SOURCE(CATALOG) command.

Members that are not affected by the member OLC are not quiesced.

You can make online changes to the ACB library in IMSplex environments in which:

• A single IMS system comprises the IMSplex. In this configuration, IMS must use the OLCSTAT data set with a CSL that consists of an OM and SCI. An RM is not required.
• Multiple IMS systems comprise the IMSplex. In this configuration, each IMS system must use the same shared OLCSTAT data set, or each system must use its own local OLCSTAT data set. The CSL must consist of an OM, an SCI, and an RM. Although a resource structure is recommended, it is not required.

Global online change for ACBLIB members can only be performed in an IMSplex.

You can specify whether the ACBLIB member is shared or dedicated in the IMSplex. The following example highlights how the ACBLIB member online change process can be coordinated among all IMS systems that share the OLCSTAT data set:

• OM chooses an IMS system to be the command master IMS.
• The command master IMS coordinates the member OLC process with other IMS systems sharing the OLCSTAT data set using RM.
• ACBSHR= must be specified as Y or N in the DFSCGxxx or DFSDFxxx PROCLIB member.
  • Y– Indicates that all of the IMS systems in the OLCSTAT are using the same active and inactive ACBLIB.
  • N– Indicates that each IMS in the OLCSTAT is using its own dedicated active and inactive ACBLIB.
• All IMS systems in the IMSplex that share the OLCSTAT data set must specify the value of ACBSHR=.
• The member OLC updates all the active ACBLIBs, whether or not they are shared.

The ACB member online change uses IMS type-2 commands only. The commands that are involved in performing an ACB library member online change are:

• INITITATE OLC PHASE(PREPARE)
• INITIATE OLC PHASE(COMMIT)
• TERMINATE OLC
• QUERY MEMBER TYPE(IMS)
• QUERY OLC SHOW(RSCLIST)

See Changing or adding IMS.ACBLIB members online for the steps required to perform an ACB member online change. If you want to fall back to the previous version of the changed resource, perform a full online change process with a full library switch.