Re: Oracle on AIX hangs

   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 aixtips.com which looks possibly relevant. Basically Maxperm
>does not restrict memory usage alone.
>
>http://www.circle4.com/jaqui/eserver/aixtra-May05-TuningJFS2.pdf
>
>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: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]
>On Behalf Of Allen, Brandon
>Sent: 26 January 2006 22:33
>To: Paul G Parker; oracle-l_at_freelists.org; MARK BRINSMEAD
>Subject: RE: Oracle on AIX hangs
>
>Yes, minperm 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: parkerpg_at_gmail.com [mailto:parkerpg_at_gmail.com]On Behalf Of Paul G
>Parker
>Sent: Thursday, January 26, 2006 3:19 PM
>To: Allen, Brandon; oracle-l_at_freelists.org
>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 www.aixtips.com
>
>Paul
>
>
>
>On 1/26/06, Allen, Brandon <Brandon.Allen_at_oneneck.com> 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 the paging.
>
>Thanks,
>Brandon
>
>
>-----Original Message-----
>From: parkerpg_at_gmail.com [mailto:parkerpg_at_gmail.com]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
>
>
>
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