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Consultation for changing the parameter MEMORY_TARGET

Posted on 2015-01-12
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Hi experts,
In a RAC ASM 11g, Linux  (RedHat  2.6.18), with 2 instance, I need to modify:
memory_max_target parameters (static parameter) 
memory_target (dynamic).

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Both in 8G ( currently have 6G)
I received a recommendation that tells me tweak in /etc/fstab:
 /dev/shm ----> defaults, size = 8G,

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and then:
mount -o remount / dev / shm

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In addition to the statements:
ALTER SYSTEM SET MEMORY_MAX_TARGET = 7680M SCOPE = SPFILE; 
ALTER SYSTEM SET MEMORY_TARGET = 7680M SCOPE = SPFILE; 

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then, in both nodes:
shutdown immediate
startup

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Currently the line in fstab says:
tmpfs /dev/shm tmpfs defaults, nosuid, nodev 0 0

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Is it necessary to make this change in the fstab?
Would appreciate a look from you and the basic steps to perform the task.
Thank you very much
Regards
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Question by:carlino70
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6 Comments
 
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Expert Comment

by:sdstuber
ID: 40545068
yes, you need to make your tmpfs large enough to hold your MEMORY_MAX_TARGET.

You are trying to hold 7.6G of oracle memory inside 6G of allocation.

my guess is you are seeing ORA-00845 errors because of this.

So, make /dev/shm larger or your memory_max_target lower
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Author Comment

by:carlino70
ID: 40545136
I'm not seeing errors like ORA-00845 in AlertLog
But if the base, shows slow queries and runs Oracle jobs.
Thanks
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Author Comment

by:carlino70
ID: 40545142
sorry, I wrote bad:
But the database, shows slow queries and runs Oracle jobs.
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Accepted Solution

by:
sdstuber earned 2000 total points
ID: 40545149
The instance shouldn't start if you have memory_target (or max_memory_target) of 7.6G with only 6G of shared memory.

Maybe I misunderstood what you posted above, are all of those code boxes suggestions or are some of them what you currently have?

I thought the 8G change was the suggestion and the rest was what you actually had, in which case I would expect an error.


If all of it is a suggestion, then yes, go with that.  It should work.
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Author Closing Comment

by:carlino70
ID: 40545166
Excellent!, Thanks
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LVL 74

Expert Comment

by:sdstuber
ID: 40545168
Glad I could help.

Making sure your shared memory at the OS level is big enough for the instance's memory is just an extension of the same thing you would have had to do when the database was created.

Configuring /dev/shm to be big enough is one of the preinstallation requirements

http://docs.oracle.com/cd/E11882_01/install.112/e47689/pre_install.htm#LADBI1096

Here you're already installed, but if you're making your instance bigger, then same idea as the preinstall.  You must also make the /dev/shm big enough to hold it.
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