Monitoring the usable space in your RACF database

Over time, the usable space in a data set in your RACF® database decreases in two ways:

As new profiles are added to the data set, the amount of available space decreases.
As existing profiles are updated, the available space might become fragmented. When an existing profile is updated, there might not be enough room to update it in its current position in the data set, and it might have to be rewritten in a larger contiguous slot. Therefore, a data set that appears to have plenty of available space might be so fragmented that an update to a profile fails due to insufficient space because there is not a large enough contiguous slot to accommodate it.

In order to anticipate and prevent running out of usable space in your RACF database, periodically run the RACF database verification utility, IRRUT200, against each data set in the database, to check on the amount of available space and its degree of fragmentation. The MAP ALL function of IRRUT200 reports the percentage of the data set that is in use and produces an encoded map of the BAM (block availability mask) blocks that is useful in determining if the data set has become fragmented. For more information on running IRRUT200, see RACF database verification utility program (IRRUT200).

When you determine that your usable space is running low, run the RACF database split/merge/extend utility program, IRRUT400, to copy your data set to a larger data set, or, if fragmentation is the only problem, to another data set the same size. As IRRUT400 copies the data set, it rebuilds it, undoing any fragmentation that has occurred. For a procedure to follow to do the copy, see Copying your database and follow the instructions there using IRRUT400. For information about IRRUT400, see RACF database split/merge/extend utility program (IRRUT400).