Re: Using AMM with Linux RAC

Hi Sherrie,

The memory which is reserved for PGA_AGGREGATE_TARGET will not show up in
/dev/shm as it's not shared (PGAs are still allocated using process-private
memory).

You can query V$MEMORY_DYNAMIC_COMPONENTS to see how Oracle is currently
using the memory:

SQL> select component, current_size from v$memory_dynamic_components where
component like '%Target%';

COMPONENT                      CURRENT_SIZE
------------------------------ ------------
SGA Target                        545259520
PGA Target                        293601280


Note that hugepages are not used with AMM on Linux so you may be not getting
all the performance out of your hardware...

--
Tanel Poder
http://tech.e2sn.com
http://blog.tanelpoder.com


On Thu, Feb 18, 2010 at 9:51 PM, Sherrie Kubis <
Sherrie.Kubis@xxxxxxxxxxxxxxxxxx> wrote:

>  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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