Hi, Since nobody else went in for the big explanation I thought I might.
AIX memory tuning can help TSM performance significantly. We run on RAW LVs and set the AIX box to not page at all. >From our experience, the key seems to be the paging of the bufferpool. TSM keeps this cache of DB pages in memory to speed things up, if they end up put back on disk (usually slower system disks) then the advantage is lost, even if the cache hit% is high, the performance will be low as the system disk and the paging space on it becomes the bottleneck. My understanding is that AIX memory gets divded up into two types: computational (application code/storage) and non-computational/file (basically jfs file caching). The minperm/maxperm settings determine which of these gets paged out when AIX gets short on memory. When computational pages get paged out they go to the paging space, when non-computational pages get paged out they go back to their backing disk storage, where they came from. To stop the system paging out the TSM bufferpool, we found the right balance for our systems. This involved working out how much various applications used and setting the minperm/maxperm to match. For example, a theoretical system with 2GB may use memory in the following way: 512MB - AIX + local apps (about right on our hosts) 512MB - TSM bufferpool 512MB - TSM code etc ???MB - AIX file caching The aim would then be to tune the system so that it always had at least 1.5GB of computational memory available. That way TSM should never get paged out. To do this on this system would require setting the maxperm/minperm combination to something like 20/10, meaning 80% (5% "breathing" space) of memory should remain computational (AIX, TSM, the TSM bufferpool etc) and a max of 20% for AIX's file caching. With these settings when AIX gets a little short on memory it should eat into the file cache and not the TSM bufferpool. If you don't use RAW LVs for your LOG/DB/DISK STGPOOLS then you have an added factor to think about. The JFS file caching (non-computational) may actually be helping you, it is another layer of caching being utilised before the data hits the physical media. Careful consideration needs to be given to how much room to give to this (especially if it helps with STGPOOL which doesn't get its own bufferpool). For better explanations and a better overview on AIX performance: AIX 5L Performance Tools Handbook http://www.redbooks.ibm.com/abstracts/sg246039.html Sorry for the long post, Pete -- Peter Jones Unix Systems Programmer (HFS) Oxford University Computing Services