On Thu, 2 Feb 2012 13:42:45 -0500, Jim Mulder <d10j...@us.ibm.com> wrote:
>> >I wonder what if any studies on this have been done in the lab. >> >It would be nice if an IBM performance expert like Kathy Walsh >> >could weigh in. Thanks for jumping in Jim! I hoped you or Peter would eventually to clear up some of this FUD. > > The last performance studies I remember for paging were >around the time of MVS XA/SP2.2.0. Very little has been done >in the area of paging performance since then except for the >PAV stuff to allow two concurrent operations to a page data set. > Even though "zero" demand paging is best and what many shops strive / configure for these days, I think it's time for a new study based on modern architecture and what the OS now does. > > The page data set selection algorithm considers service time for >the devices, but not the full percentage. One could argue that >the full percentage should be considered, since it affects the >likihood of finding contiguous slots, and the CPU time to find >available slots, but that is not how it currently works. I'm going to take a giant leap of faith here and say there is zero to negligible performance impact in having a farm of 3390-27 local page datasets running at 50% full compared to having them at 30% (or less). Maybe 69% is fine too. No higher - we certainly don't want to hit that 70% MCCASMT1 threshold! :-) Regards, Mark -- Mark Zelden - Zelden Consulting Services - z/OS, OS/390 and MVS mailto:m...@mzelden.com Mark's MVS Utilities: http://www.mzelden.com/mvsutil.html Systems Programming expert at http://expertanswercenter.techtarget.com/ ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
