>We ran into something like this when we went from 4.4 to 5.1. We actually > ran out of page space. IBM >pointed us to a page in a manual that said we should have enough page spa >ce for the sum of the size >all our virtual machines. We "Bit" the bullet and got more page packs. I >don't remember details, but >there were algorithm changes in 5.1. Once we added the page packs, I don't > remember any actual problems with it.
At the time, we had 16 3390-3 volumes dedicated to paging. The calculation showed that we should have 64, but we decided to try 32. I believe we had 32G of main storage and 4G of expanded storage at the time. IBM also said that their change to the paging algorithm had been "too aggressive", and IIRC, they issued a PTF. We backed off to 4.4 until the PTF was ready, so I don't think we ever ran with the original 5.1 algorithm and 32 page volumes. We still have the 32 page volumes today, on z/VM 5.2.0 with 43G main/4G expanded. With our normal workload, the page space is 20% full.
