Dump Directories and Performance

IPCS uses a user dump directory to process dumps efficiently. IPCS determines the most efficient method of mapping storage and creating symbols for its use. IPCS and VSAM, however, sometime do not agree on the most efficient use of the dump directory. You cannot alter the IPCS code, but you can do several VSAM-related things to your dump directory to try to improve performance.

Using System-Managed Storage
To use system-managed storage, specify in the BLSDDIR CLIST the parameters: DATACLAS, MGMTCLAS, and/or STORCLAS.
Changing the Control Interval Size
One of the potential bottlenecks in IPCS processing is the number of control interval splits in the dump directory. Periodically review the rate of control interval splits your IPCS users experience. To minimize splits, adjust the NDXCISZ parameter value in the BLSCDDIR CLIST to tune the size of the index and data in the dump directory.
Copying Source Descriptions
The COPYDDIR subcommand allows VSAM to reorganize the source descriptions as it copies descriptions from one dump directory to another. To take advantage of COPYDDIR, you can modify your installation's dump management procedures as follows:
1. Have the jobs that produce initial problem screening reports save the source descriptions in the sysplex dump directory.
2. Have individual users invoke COPYDDIR to copy the source description to their own user dump directories. Not only to the users avoid IPCS initialization processing, but the source description is less fragmented.
Refreshing Dump Directories
You or an individual user can invoke the TSO/E REPRO command to copy the contents of a dump directory to a temporary data set, then back into the dump directory. This allows VSAM to reorganize the data in the dump directory. See z/OS MVS IPCS User's Guide for a sample CLIST to refresh the dump directory.
Changing the Buffer Space
You or an individual user can use the TSO/E ALTER command to change the amount of virtual storage IPCS uses to buffer the data portion of a dump directory. IPCS will override the value specified if space for less than 16 control intervals or more than 1024 control intervals is specified.