Advanced Topics › Control and Checkpoint File Considerations › Control File Size Considerations › Changing the Block Size for the Control File

Changing the Block Size for the Control File

CA MIM typically uses a block size of 6144 bytes when accessing its control file. You can use this default value when accessing any type of DASD. We recommend that you use this block size unless you receive message MIM0025, indicating that a larger block size is needed.

To change the block size

1. Specify a new value for the BLKSIZE parameter on either of the following:
   • The MIMINIT statement on the PARM parameter of the startup procedure
   • The z/OS START command for CA MIM
2. Reformat your DASD control files, if necessary.

More information:

How You Format Control and Checkpoint Files.

Example: Change block size

To change the block size to 12288 bytes, specify the following MIMINIT statement in the initialization member:

MIMINIT BLKSIZE=12288

Note: In some environments, you can improve system performance by increasing the block size. This causes CA MIM to perform fewer distinct read/write operations to its control file. You may especially want to increase the block size if you are using GCMF to direct a large number of messages across systems.