z/VSE internals: Are you aware of one megabyte frames ?
Ingolf24 120000DRN3 Visits (2605)
It's again late today, but as you may know, just before vacation these are always long days.
Today I want to talk about megabyte (1 MB) frame support in z/VSE.
1 MB frames or large pages are available on z10 and zEnterprise processors. It's more an z/VSE internal item, because applications don't care about it. It's transparent to application. Usually the virtual and real storage is organized in 4 KB (page) sizes. With 1 MB frame support one MB of virtual storage is backed with a 1 MB (real) frame, if enough processor (real) storage is available. The virtual storage assign to a 1 MB frame can be viewed as being "fixed", because paging does not occur. 1 MB frame support is available in LPAR mode only.
z/VSE uses 1 MB frames to back virtual storage of data spaces. Long running applications accessing data spaces frequently might benefit from improved CPU utilization. z/VSE decides internally when and how data spaces will be backed with 1 MB frames. Therefore a data space may consist of both "fixed" and "pageable" virtual storage.
If the z/VSE system runs our of processor storage, one or more 1 MB frames used for backing data spaces will be made available again for use by the system. That is the one MB virtual storage will then be backed with 4 KB frames and now can be paged. You might increase the processor storage to avoid that situation.
All data spaces that you define with a maximum size of at least 960 KB will benefit from 1 MB frames as long as sufficient processor storage is available.
No configuration option is required.