IMS™ management of ACBs

This topic describes how FM/IMS operates when IMS™ is configured to manage the runtime application control blocks (ACBs).

When management of ACBs by IMS™ is enabled:

  • The IMS™ catalog is the trusted source for DBDs and PSBs.
  • IMS™ mostly no longer requires DBD, PSB, and ACB libraries.

In keeping with this, FM/IMS retrieves the PSBs and DBDs from the IMS catalog.

Mostly the IMS™ Catalog API (DFS3CATQ) is used to retrieve these control blocks. However, when the control blocks are required by IMS™ utilities that FM/IMS uses to provide dynamic PSB support, the IMS™ Catalog Library Builder utility (DFS3LU00) is used to retrieve them. This is because the IMS utilities require the control blocks to be in libraries.

Restriction: FM/IMS does not support accessing logical databases, as the IMS Catalog API and the IMS Catalog Library Builder utility do not support retrieval of logical DBDs.

Configuring FM/IMS when IMS™ management of ACBs is enabled

Set ACBMGMT=CATALOG on the FMN1POPI macro statement to specify that IMS™ management of ACBs is enabled.

Also set the following FMN1POPI parameters:

  • Use the BSDSHLQ parameter to specify the high level qualifier for the IMS™ bootstrap data set.
  • Use the DFSDF parameter to specify the 3-character suffix of the DFSDFxxx member of the IMS™ PROCLIB data set that contains the settings and attributes of the IMS™ catalog.
  • Use the PROCLIB parameter to specify the name of the IMS™ PROCLIB data set that contains the required DFSDFxxx member.
  • Use the REGCATLG parameter to specify whether the IMS catalog is registered with DBRC.

For more information on how to code these parameters, see FM/IMS options.

Note: The DBDLIBn, DBRC, and PSBLIBn parameters are not used when IMS management of ACBs is enabled.

Dynamic PSB support when IMS™ management of ACBs is enabled

Dynamic PSBs are supported differently when IMS management of ACBs is enabled.

FM/IMS supports two methods of generating dynamic PSBs when IMS management of ACBs is enabled.
Method 1
Dynamic PSBs are generated by submitting Data Definition Language (DDL) statements to the IMS Data Definition utility. If you plan to use this method, set USEDDL=Y on the FMN1POPI macro statement. For more information on using this method, see USEDDL.
Method 2
Dynamic PSBs are generated by submitting macro instructions to the PSB Generation utility. If you plan to use this method, set USEDDL=N on the FMN1POPI macro statement.
IMS management of ACBs and dynamic PSB support compares Method 2 with the method used when ACBs are managed by IMS.
Table 1. IMS™ management of ACBs and dynamic PSB support
When ACBs are managed by your installation When ACBs are managed by IMS™
IMS builds the ACB for the DOPT PSB when functions are run in DLI mode. IMS does not build an ACB for the DOPT PSB when functions are run in DLI mode or BMP mode.
FM/IMS builds the ACB for the DOPT PSB when functions are run in BMP mode. FM/IMS builds an ACB for the DOPT PSB when functions run in BMP mode or DLI mode.
The ACB maintenance utility uses your installation's DBD libraries. The ACB maintenance utility uses DBD libraries that are dynamically generated by the IMS Catalog Library Builder utility.
The DOPT ACB library is concatenated with the primary ACBLIB data set in the IMS execution JCL. The IMS Catalog Populate utility adds the DOPT PSBs to the IMS catalog.
Restriction: FM/IMS adds DOPT PSBs to the IMS catalog, but it does not delete them. Therefore, periodically use the IMS Catalog Record Purge utility (DFS3PU10) to remove the DOPT PSBs from the IMS catalog.

If you plan to use this method to generate dynamic PSBs, use the DYNACB parameter to specify the name of the ACBLIB data set into which the ACB Maintenance utility generates the DOPT PSBs. You would also do this if the ACBs are managed by your installation, but when IMS management of ACBs is enabled, the specified data set is required by functions that access databases in BMP mode or in DLI mode.