Using AMM with Linux RAC

  • From: Sherrie Kubis <Sherrie.Kubis@xxxxxxxxxxxxxxxxxx>
  • To: "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
  • Date: Thu, 18 Feb 2010 08:51:14 -0500

We have a 3-node (each 32 gb ram) Linux RAC cluster running Oracle 11.1.0.7, 
housing 4 instances with a total memory_target of 8.75 gb.  OEM shows 29% ram 
is used. We are using AMM.



The free -mt command shows:



             total       used       free     shared    buffers     cached

Mem:         32189      31519        669          0       1250      25168

-/+ buffers/cache:       5101      27088

Swap:        32767         39      32728

Total:       64957      31559      33397



It looks like tmpfs is 16gb:

 df -k /dev/shm

Filesystem           1K-blocks      Used Available Use% Mounted on

tmpfs                 16481056   5604532  10876524  35% /dev/shm



We are seeing 5.6gb of memory used, so I'm confused about why the SGAs are 
defined to consume 8.75gb, but we only see 5.6gb used.  I read that the SGA, by 
default, takes 60% of memory_target and pga gets the rest. Because there are 
not yet many connections, is this why we see a lower value?



Does the tmpfs at 16gb mean we can only use 16gb of ram for our databases?



Any insights would be appreciated.  We are just starting out with Linux and 
Posix-Style shared memory management, quite different than shared semaphore 
memory segments that we were used to.


Sherrie Kubis
Southwest Florida Water Management District





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