You might look into the Virtual Lookaside Facility (VLF).
Some good introduction can be found in:
z/OS: MVS Programming: Authorized Assembler Services Guide
? Copyright IBM Corp. 1988, 2002
Document number . . : SA22-7608-03
The area in which our company is using VLF is repeatedly retrieved Rexx execs. ISPF/DM objects are localy cached so they are no good candidates for VLF.
Testing revealed an elapsed time improvement on the I/O of a factor 3.
With kind regards,