Buffer pool control blocks backed by 1MB frames
agburke 060001QPDN Visits (2020)
PM85944 allwed the buffer pool PMB (page manipulation blocks) to be backed by pageable 1MB frames. The only way for DB2 to utilize pageable 1MB large frames is if you have FlashExpress installed on your zEC12 or zBC12 running z/OS 1.13 with FMID JBB778H applied. For clarification, if your buffer pools are page fixed and backed by LFAREA (amount of real storage set aside for 1MB frames) in DB2 10 or DB2 11 then the PMBs are already backed by 1MB frames. Thus the addition of Flash Express would not help. If however you cannot afford the real memory to page fix the buffer pools and back them with LFAREA then the addition of Flash Express could help with the TLB misses (CPU performance). In this case the PMBs would be backed by non-LFAREA storage, but you should have some spare LFAREA storage set aside, because if we run out of non-LFAREA then performance would still be better if we fell back to LFAREA, rather than actually paging to the Flash storage.