The IMS catalog in multi-system configurations

In a multi-system environment, all of the IMS systems can share a single IMS catalog, each IMS system can have its own IMS catalog, or some IMS systems can share while and other systems can have their own.

Similarly, the resources that are associated with the IMS catalog, such as ACB libraries and DFSDFxxx members of the IMS.PROCLIB data set, can be shared by some IMS systems, all IMS systems, or no IMS systems.

To share an IMS catalog, DBRC and the configuration of a data sharing environment is required.

Recommendation: If your IMS systems share databases, have them share an IMS catalog as well. Keeping common metadata in sync across independent IMS catalogs can be difficult and is prone to error. Sharing reduces complexity.

When the IMS management of ACBs is enabled for an IMS system, the IMS catalog assumes the role of the ACB library for that system. The system no longer uses ACB, DBD, and PSB libraries. The sharing of ACBs is determined by the sharing of the IMS catalog and the specification of the ACBSHR parameter in the DFSCGxxx member or in the COMMON_SERVICE_LAYER section of the DFSDFxxx member of the PROCLIB data set. If an IMS system requires a different set of ACBs than other IMS systems in a multi-system environment, the IMS system must use its own IMS catalog.

Each IMS catalog must have an alias name. The alias name is specified in the DFSDFxxx member on the ALIAS parameter. If you use multiple IMS catalogs, each alias name must be different. If you use only a single IMS catalog and do not need to use an alias name, specify the default catalog prefix, DFSC, as the alias name.

If the RECON data sets are shared, but IMS catalogs are not shared, when the IMS catalog databases are registered with DBRC, they must be defined in the RECON data set by using their alias names. The alias name dynamically replaces the first four characters of the catalog database name and secondary index name and prevents conflicts in a multi-system environment.