Roads ? - where we're going, we don't need roads ...
Month of March, 2011 | ORA600
ORA600 content Content RSS
Oracle ORA600 News RRSS Oracle News RSS
ORA600 blog Blog RSS
ORA600 blog Blog Atom

User login

Month of March, 2011

Memory Footprint For Dedicated Server Processes More Than Doubled After 11g Upgrade On AIX Platform

Another one I categorize under 'I should write this down before I forget'.
Connor Mcdonald - Oracle geek and entertainer extraordinaire - shared this with me last week. Apparently, he was having some memory issues after upgrading to 11gR2 under AIX. As we run 80% of our databases under AIX, I thought I should make a mental note about it (some may call it a blogentry).
For those with metalink access - lookup note id ID 1246995.1 titled 'Memory footprint for dedicated server processes more than doubled after 11g upgrade on AIX platform'.
 

The symptoms are :
  • excessive memory utilization for dedicated server process after upgrade to 11.2.0.1 or 11.2.0.2 on AIX
  • svmon on oracle OS process id shows size of USLA, User-Space Loader Assistant, heap of about 7M bytes
 
 
Example 
svmon -P <PID>
outputs
  • 11.2.0.1.0 -> 7M bytes (=USLA x 4k page size)
  • 11.1.0.7.0 -> 60KB 
  • 10.2.0.4.0 -> 420KB

Example on 11.2.0.1 (unpatched)
 svmon -P 1368120 | grep USLA
 10e811d  9fffffff clnt USLA text,/dev/hd2:8227      s     17     0    -       -
 10d89b9  80020014 work USLA heap                   sm      0     0 1895    1895 ---> x4K = 7Mb
 
Example on 11.2.0.1 (patched)
  c291c2  80020014 work USLA heap                   sm     31     0    0      31 ---> x4K = 124K
 
 
 
This is apparently a bug
Bug 10211065.-P Base Bug 9796810
Abstract: MEMORY FOOTPRINT FOR DEDICATED SERVER PROCESSES MORE THAN DOUBLED AFTER 11G UGP
 
 
Bug 9796810.-P Base Bug 10190759
Abstract: 11G SERVER PROCESSES CONSUMING MUCH MORE MEMORY THAT 10G OR 9I
 
 
Bug 10190759.-P
Abstract:  PROCESSES CONSUMING ADDITIONAL MEMORY DUE TO 'USLA HEAP'

 
 
The good news is - there's a 'interim' patch - number 10190759.
It basically changes the make file so that it excludes certain options (-bexpfull and -brtllib) related to 11g's online patching feature.
It's not really an Oracle problem but it seems related to a bug in runtime loader on AIX.
 
 

_memory_imm_mode_without_autosga - no really ! don't resize my sga ! I mean it !

Wow - I need a mental note for this one ! (hence the blogpost)

So you've disable Automatic Memory Management (AMM/ASMM) on your new 11.2 instance - memory_target and sga_target are set to zero ... because ... the dba knows best!
You've configure large pages - locked the sga in memory - manual configured buffercache etc - you've got the luxury of finally having a machine with gigs and gigs of memory.

And then one day you find out that your buffercache is 256Mb in size, the large pool is now 20Gb (coming from 1Gb) and the alert file is screaming ORA-4031, ORA-4031 !!!

How did that happen !!!!!! We didn't use automatic memory management ! You scream and yell - who touched the instance parameters..... no fool would set a large pool of 20Gb and a buffer cache of 256Mb manually.
Looking in the audit logs reveals nobody touched the instance ... it seems AMM/ASMM *is* at play - how can that be if we disabled it ?

You open a SR with support and everything becomes clear now :
- we just ignore your settings and do AMM anyway - if you don't want that set this underscore parameter :
alter system set "_memory_imm_mode_without_autosga"=FALSE scope=both;

Quote - "This is expected behavior in 11.2 for immediate memory allocation requests, which added this as a new feature when automatic memory management was disabled."
Stupid me !
 
note on metalink "SGA Re-Sizes Occurring Despite AMM/ASMM Being Disabled (MEMORY_TARGET/SGA_TARGET=0) [ID 1269139.1]"



Howto's
See DUDE primer for info

Get Support

Europe

Belgium :
Kurt Van Meerbeeck
ORA600 bvba
E-mail
dude@ora600.be
Cell : +32 495 580714

Denmark :
Michael Môller
Service & Support Manager
Miracle AS
E-mail :
hra@miracleas.dk
Cell: +45 53 74 71 27


North America

USA :
Tim Gorman
Evdbt Inc
E-mail
tim@evdbt.com
Cell : +1 303 885 4526

Canada :
Pythian
E-mail
dude@pythian.com
Contact


Latin America

Brazil :
HBtec
E-mail
dude@hbtec.com.br
Cell : +55 47 88497639
Contact


Africa

South Africa :
Kugendran Naidoo
NRG Consulting
E-mail
k@nrgc.co.za
Cell : +27 82 7799275


East Asia Pacific

Australia
Andre Araujo
Pythian Australia
E-mail
dude@pythian.com
Cell : +61 2 9191 7427 ext. 1270