Adjusting VSAM options

For VSAM, you can adjust options specified in the OPTIONS control statement and options specified in the Access Method Services DEFINE CLUSTER command.

The only VSAM option you can specifically monitor for is background write. If you are not using background write, you can look at the VSAM Buffer Pool report described in IMS Version 15.4 System Administration. The report, in the Number of VSAM Writes To Make Space in the Pool field, documents the number of times data in a buffer had to be written to the database before the buffer could be used. If you use background write, you might find that you are able to reduce this number and therefore the size of the buffer pool.

If you are already using background write, the VSAM Buffer Pool report tells you how many times background write is invoked in the Number of Times Background Write Function Invoked field. The VSAM Statistics report (another report produced by the DB monitor) tells you in the BKG WTS field if background write was invoked. It also tells you, in the USR WRTS field, among other things, how many times background write was invoked.