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Re: Oracle on AIX hangs

From: Fuad Arshad <>
Date: Sat, 28 Jan 2006 07:10:35 -0800 (PST)
Message-ID: <>

i would certainly agree. even if you are moving from raw to filesystems.   jfs2 with cio certainly gives you a lot of benefits

Mark Brinsmead <> wrote:

     That link certainly is a good resource. Just a caution to casual readers, though, the the particular settings described in that article don't necessarily describe what you would really want on an Oracle database server. (On my servers, where I still use JFS, I usually set minperm/maxperm to something in the range of 5/10 to 10/20.)

   Anyway, there are definitely useful tips for JFS2 users. An important JFS2 tip that is relevant to Oracle servers is "concurrent I/O" (CIO). JFS2 users who use concurrent I/O may find that their settings of minperm/maxperm/maxclient/whatever are almost irrelevant (okay, those are brave words!) because database I/O will bypass filesystem buffers entirely...

   On AIX with JFS2, CIO is definitely your friend. Or, at least, that's been my experience...

Adrian wrote:
Brandon, As previously discussed, I also have these issues periodically. Found this from which looks possibly relevant. Basically Maxperm does not restrict memory usage alone. Like most UNIX systems, AIX leaves in memory the pages-from local JFS, JFS2 or remote (NFS) file systems-of files that have been read or written. If they're referenced again, it saves an I/O operation, as they're already in memory. Since reads usually involve just a pagein-whereas computational- or workingset pages tend to involve both a pagein and a pageout-it's useful to tweak the minperm and maxperm values to favor computational pages. However, maxperm only affects JFS. JFS2's correct parameter is maxclient and many I/O problems that I look at involve misunderstandings about this parameter. For JFS, maxperm specifies the file-page value (%) above which the page stealer should steal only file pages. The  default
 is 80 percent, but this isn't a hard limit. If you set maxperm to 30 percent and the pages are available, I/O can still use up to 100 percent of memory. What you're changing is which pages get stolen when a page is needed. On the other end of the scale, minperm specifies the file-page value (%) below which the page stealer steals both file and computational pages. When the percentage of file pages falls between minperm and maxperm, the page stealer steals file pages unless the number of file repages exceeds the number of computational repages. Not at work, so cant check my settings, but looks like the maxperm may not restrict memory as expected without tweaking strict_maxclient. HTH Adrian -----Original Message----- From: [] On Behalf Of Allen, Brandon Sent: 26 January 2006 22:33 To: Paul G Parker;; MARK BRINSMEAD Subject: RE: Oracle on AIX hangs Yes, min  perm and

 maxperm have been restricted:    /usr/sbin ->vmstat -v|grep perm        10.0 minperm percentage        20.0 maxperm percentage    hdisk0 contains the swap space and it appears we were paging/swapping to  death:    /usr/sbin ->lsps -a  Page Space      Physical Volume   Volume Group    Size %Used Active  Auto  Type  hd6             hdisk0            rootvg       10240MB     1     yes   yes  l    /opt/oracle ->vmstat 15  System Configuration: lcpu=4 mem=15808MB  kthr       memory              page              faults           cpu  -----   -----------   ------------------------  ------------    -----------   r  b   avm      fre  re  pi   po   fr    sr cy in   sy    cs    us sy id wa   2  7   4965756   27   0   2    2  437   514  0 1388 30629 13078 11  5 73 11   1  180 4985880  503   0  56 1278 1411  1971  0 1311  5568  2984 27  4  0 69   2  184 4998310    0   0  36  741  853 10011  0 1250  6287  1733 28  3  0 69   1  184 5015464    0   0  44 1069 1228 10090  0 1283  4044  2431 
 28  3  0
 69   1  190 5019796  527   0  43  349  341   382  0 1216  3377  1323 27  1  0 71   1  200 5031743  277   0  41  743  819   951  0 1225  2585  1924 27  2  0 71      Now to figure out why . . .    Thanks,  Brandon      -----Original Message-----  From: []On Behalf Of Paul G  Parker  Sent: Thursday, January 26, 2006 3:19 PM  To: Allen, Brandon;  Subject: Re: Oracle on AIX hangs      Brandon,  The default settings on AIX for Virtual Memory Management are inappropriate  for a database server.    Confirm the settings of minperm and maxperm (use vmstat -v) and check out  Metalink note:  316533.1    Another useful site reference is      Paul        On 1/26/06, Allen, Brandon <> wrote:  Yes, I think you might be right - see attached.  Unfortunately I didn't save  the output of lsps, but I did run it and I'm pretty sure it said 49% used.  Now we just need to find the cause of th
 paging.    Thanks,  Brandon      -----Original Message-----  From: []On Behalf Of Paul G  Parker  Sent: Thursday, January 26, 2006 2:29 PM  To: Allen, Brandon  Subject: Re: Oracle on AIX hangs      Brandon,    My guess would be excessive paging.  What is the output of lsps -a ?  Do you have any vmstat output during this "hang"?    Paul        Privileged/Confidential Information may be contained in this message or  attachments hereto. Please advise immediately if you or your employer do not  consent to Internet email for messages of this kind. Opinions, conclusions  and other information in this message that do not relate to the official  business of this company shall be understood as neither given nor endorsed  by it.   --      --            


Received on Sat Jan 28 2006 - 09:10:35 CST

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