For many years the price of z/OS memory has been decreasing, and IBM has been pushing the idea of large amounts of memory. DB2® for z/OS has virtually eliminated its virtual storage constraints.
DB2 performs best when it has lots of memory (i.e. real memory). Memory is still not free, but large memory can save money by reducing CPU consumption while at the same time reducing DB2 transaction response time. More memory also increases DB2 availability in cases where it is necessary to dump the DB2 address space, because if dumping causes paging to occur, the dump will take longer, and DB2 is not available during that time.
DB2 Buffer Pool Analyzer for z/OS
The first thing that comes to mind for the use of large memory is to increase the size of DB2 buffer pools. This can reduce the number of synchronous I/Os by increasing the buffer hit ratio. Furthermore, reducing the number of synchronous I/Os will reduce CPU consumption, because I/Os cost CPU time.