You can use the IRRUT400 utility to repair or reorganize a database that has errors in its upper level index blocks or has fragmented data. In most cases you should use IRRUT200 for copying a database if the database copy is the same size and on a device with the same track geometry. However, when IRRUT200 detects errors on upper level blocks only or an analysis of the IRRUT200 BAM block mappings shows that significant fragmentation has occurred, use IRRUT400 to perform the copy.

In all circumstances you should use IRRUT400 to repair and reorganize the database. When you use IRRUT400 to copy a database, the utility rebuilds the database, recreating upper level index blocks and reorganizing profiles to prevent fragmentation. The profile reorganization makes all the segments of a single profile (for example, a user profile's base, TSO, and CICS® segments) contiguous.

Reorganizing the database can improve performance by reducing the number of database reads required to read profiles. As a profile continues to be updated, its segments are likely to be written to different physical blocks in the database. You can see this in the output in Figure 1, noting the RBA of each profile segment. RACF® reads the database one 4K block at a time. If the segments are spread across fewer 4K blocks, fewer reads are required to access them, providing better performance of RACF functions that require database profile access.