On Tue, 11 Apr 2017 10:46:40 -0400, Pinnacle <[email protected]> wrote:
>Gone are the halcyon days when we could run an LPAR with three mod-3's >as the local paging subsystem. With today's large memory sizes, I'm >faced with having to completely rethink my paging subsystems. I've >currently got a 133GB LPAR with 18 mod-9 locals at 44%. I'm going to >add 22 more mod-9's, which will get me just under the 30% threshold. >That's 40 page datasets, which is about 30 more than the most I've ever >managed. I'm thinking about going to 10 mod-54's as my final solution >for this LPAR (roughly 4x the real memory). I wondered what the rest of >you are doing with your paging subsystems in the era of bigass memory sizes. > >Regards, >Tom Conley > The 3 largest LPARs in terms of memory in one of the sysplexes I support are: 286G, running dev WebSphere and 2 prod WAS LPARs each with 230G. I know there is not enough locals to cover all these 64-bit workloads actually using what their potential is - but then again, I don't have enough DASD of that in the entire DASD farm. We try not to page on those prod LPARs so there is enough real storage to support that and the local page DS usage is near 0%. There are 9 3390-27 locals on those 2 prod LPARs. OTOH, the dev LPAR with 286G has a larger virtual storage requirement due to so many dev WAS regions. There are 16 mod 27s for locals and right now the usage is 6%. Other LPARs in the sysplex running CICS, DB2, MQ and most of of the batch have an average of about 80G of real storage and 7-10 locals, all 3390 mod 27s. There is no way you could possible plan for worse case scenarios with 64-bit. I think you have to look at what your actual workloads are and what happens during "bad" events (like multiple SVC dumps) to have extra storage available for that so paging doesn't go through the roof. (I wish we had flash in our z13s for SVC dumps, but we don't). We do keep page ds usage at 30% or lower per the old ROT and I still see that ROT sited. But honestly, I don't get it... with mod-27s and mod-54s for locals, how could ASM not find enough contiguous slots to be efficient even if the page DS is 50% utilized. Best Regards, Mark -- Mark Zelden - Zelden Consulting Services - z/OS, OS/390 and MVS ITIL v3 Foundation Certified mailto:[email protected] Mark's MVS Utilities: http://www.mzelden.com/mvsutil.html Systems Programming expert at http://search390.techtarget.com/ateExperts/ ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
