Topic
7 replies Latest Post - ‏2014-03-18T04:40:38Z by RajasekharVG
SystemAdmin
SystemAdmin
6908 Posts
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Pinned topic AIX use SWAP but don't use all RAM memory

‏2012-10-31T09:16:30Z |
Hello

I'm using AIX 6.1 for Oracle 10g (10.2.0.5) database (3,5 GB for SGA and 0,7 for PGA).
When I run nmon AIX is using 17% of SWAP but it don't use 13 % of free RAM memory (look on the picture)
Belov output from vmo -a

root@prod1-1-szi:/root$ vmo -a

ame_cpus_per_pool = n/a
ame_maxfree_mem = n/a
ame_min_ucpool_size = n/a
ame_minfree_mem = n/a
ams_loan_policy = n/a
force_relalias_lite = 0
kernel_heap_psize = 65536
lgpg_regions = 251
lgpg_size = 16777216
low_ps_handling = 1
maxfree = 1088
maxperm = 443232
maxpin = 599436
maxpin% = 53
memory_frames = 2097152
memplace_data = 2
memplace_mapped_file = 2
memplace_shm_anonymous = 2
memplace_shm_named = 2
memplace_stack = 2
memplace_text = 2
memplace_unmapped_file = 2
minfree = 960
minperm = 29548
minperm% = 3
nokilluid = 0
npskill = 20480
npswarn = 81920
numpsblks = 2621440
pinnable_frames = 487575
relalias_percentage = 0
scrub = 0
v_pinshm = 1
vmm_default_pspa = 0
wlm_memlimit_nonpg = 1

I use ora_mem.pl scrip to analyze what kind of memory was used for oracle processes. (Summary of teh output is on the picture)

I don't know why AIX don't use RAM ?
Updated on 2012-11-01T23:24:54Z at 2012-11-01T23:24:54Z by Holgervk
  • alethad
    alethad
    286 Posts
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    Re: AIX use SWAP but don't use all RAM memory

    ‏2012-10-31T15:46:02Z  in response to SystemAdmin
    I'm not sure I understand your question.

    Are you asking why the OS doesn't use up ALL the RAM that the apps aren't using? If this is your question then the OS isn't designed to use ALL the RAM. It takes what it needs and leaves the rest.

    Oracle is designed to run in RAM if you configure it to do that. It isn't required but most admins prefer it. Even then I'm not sure the Oracle will take the rest for itself from what I've seen on my Oracle systems.
    You don't want to run out of RAM or your system may have severe performance issues.

    Or re-ask your question if I'm not understanding you correctly.
    You've got to continue to grow, or you're just like last night's cornbread -- stale & dry Loretta Lynn alethad
  • dukessd
    dukessd
    337 Posts
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    Re: AIX use SWAP but don't use all RAM memory

    ‏2012-11-01T00:30:50Z  in response to SystemAdmin
    I think there is an APAR for that, have a google for it, or call IBM and get a PMR opened up to ask them to check out a perfpmr and they'll let you know why it is paging with so much free memory available - and then they'll let you know the APAR you need.
  • DnShaver
    DnShaver
    4 Posts
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    Re: AIX use SWAP but don't use all RAM memory

    ‏2012-11-01T01:20:15Z  in response to SystemAdmin
    APARs for AIX 61
    REL APAR Defect ServicePack Abstract
    61N IZ98552 793205 6100-06-07_SP PAGING TO PAGE SPACE ON PROPERLY TUNED SYSTEM.
    61Q IV07461 793205 6100-07-02_SP Reduce early working storage paging
    61S IV07461 793205 6100-07-04_SP PAGING TO PAGE SPACE ON PROPERLY TUNED SYSTEM.
    APARs for AIX 71
    REL APAR Defect ServicePack Abstract
    71B IV14641 793205 7100-00-05_SP PAGING TO PAGE SPACE ON PROPERLY TUNED SYSTEM.
    71D IV09238 793205 7100-01-03_SP Reduce early working storage paging
    71F IV09238 793205 7100-01-04_SP PAGING TO PAGE SPACE ON PROPERLY TUNED SYSTEM.
  • SystemAdmin
    SystemAdmin
    6908 Posts
    ACCEPTED ANSWER

    Re: AIX use SWAP but don't use all RAM memory

    ‏2012-11-01T14:19:15Z  in response to SystemAdmin
    Thank you all for your answers
    I found on metalink :

    AIX: Paging Space Growth May Occur Unexpectedly With 64K (medium) Pages Enabled http://ID 1088076.1
    They are writting about APARs http://www-01.ibm.com/support/docview.wss?uid=isg1IZ71191

    I don't have installed this APAR on my AIX , (by the way I'm just Oracla DBA and this ist my first cnntact with AIX)

    DnShaver, You written also about dedicated APARs - I'm a little confused because You written about different APARs then I found in Oracle metalink , I don't know which is the best or maybe all of them.

    I can give you some additional information about this system :

    + Oracle parameter LOCK_SGA is set to TRUE
    + This is a RAC database (the second node has more memory because there are 2 additional single instances -and the effect with "don't using all RAM but pagging" does not appear)

    I check the parameter maxpin - it is 53% , but when i enumerated it from formula (RAM - SGA)*100/8 +3 it give me 59% (prabobly at first time this parameter was enumerated for SGA = 4 GB)
    Also the parameter lgpg_regions is set not properly (it is 251) it should by 219 (SGA/16MB)

    Today is a holiday in Poland so I can't change above parameters , I do that tommorow.

    Maybe you know some thing more about which APARs are the right for my situation or have some more practice with AIX tuning for Oracle :)

    Belove output from vmstat -P all (maybe this give you some additional information)
    System configuration: mem=8192MB

    pgsz memory page

    --------------------------
    siz avm fre re pi po fr sr cy
    4K 159840 1282454 1027 0 176 108 308 988 0
    64K 56826 40266 16560 0 0 0 0 0 0
    16M 251 220 31 0 0 0 0 0 0
    One question more: how to interpret the value of page_faults in nmon tool ?
    • DnShaver
      DnShaver
      4 Posts
      ACCEPTED ANSWER

      Re: AIX use SWAP but don't use all RAM memory

      ‏2012-11-01T20:31:32Z  in response to SystemAdmin
      My apologies, I was in a bit of a hurry when i responded and didn't have time to dig into this for you.

      However, it would be really handy to have the oslevel of you aix instance in order to help. My guess is that you are having an issue similar to one I encountered when upgrading to 6.1 TL7 SP5. Not all of the memory was consumed, which by default AIX can/will do, but SWAP was being used...

      We resolved this by calling IBM support and getting the vmo setting :numperm_global = "0": from them. This instantly stopped the ongoing consumption of SWAP and eventaully it did go back down to normal.

      vmo -p -o numperm_global=0

      I would not make this change without confirming with IBM that this is the best method to resolve your issue though.

      Hope this helps...

      -d
  • Holgervk
    Holgervk
    56 Posts
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    Re: AIX use SWAP but don't use all RAM memory

    ‏2012-11-01T23:24:54Z  in response to SystemAdmin
    The fact that paging-space is used but there is free memory does not always show a problem.

    Imagine your system has 100G Ram and 100G paging-space.

    The application(s) use 120G Ram... thus 100G Ram and 20G paging-space will be used.
    The application(s) then free up 40G Ram... now there will be 20G of free Ram but also 20G of used paging-space.
    • RajasekharVG
      RajasekharVG
      1 Post
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      Re: AIX use SWAP but don't use all RAM memory

      ‏2014-03-18T04:40:38Z  in response to Holgervk

      Hi , This one is called as " early paging space Allocation" bug with AIX 6.1 TL 7

      There are three different methods for the paging space allocation a) early 2) deferred 3) late ----paging space allocation

      Though we have enough amount of memory available in system to use it but it will consume some paging space

      2) Based on amount of memory allocated to system (LPAR) it will create the memory pools (by OS ) can see the output in vmstat -v (memory pools)

      Size of the memory pool should be unique for LPAR , for any reasons if the memory pool size is different , it will try to consume the total amount of memory from larger memory pool and would say all further requests can't be allocated in real memory

      All this information can be found from kdb (kernel debugger)