MSDBs storage

The MSDB Maintenance utility (DBFDBMA0) creates the MSDBINIT sequential data set in physical ascending sequence.

During a cold start, or by operator request during a normal warm start, the sequential data set MSDBINIT is read and the MSDBs are created in virtual storage. See the following figure.

Figure 1. MSDB pointers

During a warm start, the control program uses the current checkpoint data set for initialization. The MSDB Maintenance utility can also modify the contents of an old MSDBINIT data set. For warm start, the master terminal operator can request use of the IMS.MSDBINIT, rather than a checkpoint data set.

The following figure shows the MSDBINIT record format. The table following the figure explains the record parts.

Figure 2. MSDBINIT record format