Paging like this also occurred when running a paging OS under (z/)VM(/VSE). If you made the MVS space too large, VM would be paging out the least recently used frame to make room for MVS to page in an even older frame to use for the next frame.
On Wed, Aug 5, 2015 at 3:45 AM, Elardus Engelbrecht <[email protected]> wrote: > Andrew Rowley wrote: > >>I'm not sure if you can artificially limit the frames available, but I would >>expect that the effect of paging on a Java application would be BAD. Very bad. > > Of course! > > >>Java needs to perform regular garbage collection. > > A la Commodore 64 garbage collection.... I still have bad dreams of that > infamous C64 garbage collection... ;-) > > >>(I'm not sure whether z/OS is smart enought to recognise the pattern and >>bring pages back in before they are required) > > It would be interesting of z/OS can do that. Peter Relson? John Eells? Jim > Mulder? What do you say about that? > > I know IEBGENER, DFSORT and ICETOOL do their checking of storage (memory and > temp workspace) and then do with whatever is available. > > >>I wouldn't bother testing - I would just say that sufficient memory is >>required to execute in real storage. > > Agreed - actually if you have too few memory, you can't do anything. Increase > as needed and retry. > > If I want to do any testing, I will do it in a sandbox with a small > configurable memory. (CF STOR,etc.) > > >>Another consequence of this behaviour is that you should not make the Java >>heap too large. > > Good point. I have written it up in my notes. Thanks! > > Groete / Greetings > Elardus Engelbrecht > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
