Using AMM with Linux RAC

From: Sherrie Kubis <>
Date: Thu, 18 Feb 2010 08:51:14 -0500
Message-ID: <>

We have a 3-node (each 32 gb ram) Linux RAC cluster running Oracle, 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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Received on Thu Feb 18 2010 - 07:51:14 CST

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