Re: Oracle on AIX hangs
- From: Mark Brinsmead <mark.brinsmead@xxxxxxx>
- To: ade.turner@xxxxxxxxx
- Date: Fri, 27 Jan 2006 17:32:09 -0700
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...
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.
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.
-----Original Message----- From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Allen, Brandon Sent: 26 January 2006 22:33 To: Paul G Parker; oracle-l@xxxxxxxxxxxxx; 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 . . .
-----Original Message----- From: parkerpg@xxxxxxxxx [mailto:parkerpg@xxxxxxxxx]On Behalf Of Paul G Parker Sent: Thursday, January 26, 2006 3:19 PM To: Allen, Brandon; oracle-l@xxxxxxxxxxxxx Subject: Re: Oracle on AIX hangs
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
On 1/26/06, Allen, Brandon <Brandon.Allen@xxxxxxxxxxx> 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.
-----Original Message----- From: parkerpg@xxxxxxxxx [mailto:parkerpg@xxxxxxxxx]On Behalf Of Paul G Parker Sent: Thursday, January 26, 2006 2:29 PM To: Allen, Brandon Subject: Re: Oracle on AIX hangs
My guess would be excessive paging. What is the output of lsps -a ? Do you have any vmstat output during this "hang"?
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