Jim, Thank you. I thought that based on my reading but the OP said something make me wonder about it. The other question being a developer how can I guarantee a z/OS will have 64 bit storage defined so we could use it ?
Scott ford www.identityforge.com Tell me and I'll forget; show me and I may remember; involve me and I'll understand. - Chinese Proverb On Dec 8, 2012, at 2:46 PM, Jim Mulder <[email protected]> wrote: >> I am correct in assuming that the dataspace must be created by a >> running STC or JOB, and when shutsdown the dataspace Is deleted ? > > That is correct. A SCOPE=COMMON data space cannot persist > beyond the termination of its creator. > > On the other hand, 64-bit common storage is never implicitly > freed by the system, and thus can persist beyond the termination > of its creator. > > Also, starting with z/OS 1.12, z/OS turns on the common segment > bit in the Segment Table Entry for 64-bit common segments. This > cannot be done for SCOPE=COMMON data spaces. So 64-bit common > storage may incur fewer TLB misses, and use fewer TLB entries, > compared to a SCOPE=COMMON data space. > > Also, segment and page tables for data spaces are > virtualized in RSM data spaces (SYSDSxxx data spaces > owned by the RASP address space). So additional real storage > is required for segment and page tables of these RSM data spaces. > And, there may be TLB misses while accessing the page and segment > tables of the data spaces, and TLB misses while accessing > the page and segment tables of the SYSDSxxx data spaces. > > Region, segment, and page tables for 64-bit storage are not > virtualized anywhere - z/OS accesses them via real addresses. > > > > Jim Mulder z/OS System Test IBM Corp. Poughkeepsie, NY > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
