IMS directory data sets

When the IMS management of application control blocks (ACBs) is enabled, IMS stores the active ACBs in the IMS directory, a collection of system-managed data sets that are an extension of the IMS catalog. The IMS directory data sets include data sets for the ACBs that are active in the IMS system, a staging data set for ACBs that are pending activation, and a bootstrap data set that IMS uses to manage the IMS directory.

The IMS directory data sets that store the active and pending ACBs are functionally similar to the ACB library (ACBLIB) data sets that you would use to manage ACBs when the IMS management of ACBs is not enabled.

Unlike an active ACBLIB data set, the active ACB data sets of the IMS directory are system data sets that IMS creates, updates, and manages automatically. IMS automatically allocates the data sets for the IMS directory and keeps the IMS directory in sync with the IMS catalog.

When databases and program views are created or modified by using SQL DDL statements, the ACBs are generated automatically and in most cases, are stored in the staging data set of the IMS directory. However, they cannot be used until they are activated in the IMS directory.

If you are using the IMS Catalog Populate utility (DFS3PU00) to add ACBs to the IMS system, the utility can either add them to the active ACB data sets of the IMS directory when it updates the IMS catalog or the utility can save the ACBs to the staging data set. To update the active ACB data sets directly, the IMS system must be shut down.

You activate ACBs that are in the staging data set of the IMS directory by using the IMPORT DEFN SOURCE(CATALOG) command, which copies the ACBs to the active ACB data sets by using an internal process that is similar to the online change process, but simpler.

The IMS directory uses PDSE data sets for the active ACBs and the staging data set.