Re: Oracle on AIX hangs

  • From: Fuad Arshad <fuadar@xxxxxxxxx>
  • To: mark.brinsmead@xxxxxxx, ade.turner@xxxxxxxxx
  • Date: Sat, 28 Jan 2006 07:10:35 -0800 (PST)

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 <mark.brinsmead@xxxxxxx> 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 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@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, 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: 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      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@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 th
 e
 paging.    Thanks,  Brandon      -----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      Brandon,    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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