Oracle Linux RAM Usage

Hi,

Is there any level i can control the amount of memory occupied by linux for cache. Seems that most of my memory gets allocated for Cache and free memory is 0. This Server runs oracle DB.

[root@ ~]# free -g
                     total       used       free     shared    buffers     cached
Mem:            45         45                  0          0             0                 42
-/+ buffers/cache:      2               43
Swap:           23          0                23
[root@ ~]#

Is there any way i can reserve memory so that it does not take it for Caching?
GulfITAsked:
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sdstuberCommented:
linux doesn't "steal" memory for the cache, it uses what's available.

Simply use more than 45g and the os will release the cache as needed.
For example, set the memory_target higher in your database instance.

If you want, you can force the cache to release immediately, but the next disk io will start using it again if there is free memory available.


try this to see the before and after

free -g
sync;echo 3 > /proc/sys/vm/drop_caches
free -g
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GulfITAuthor Commented:
Does the memory_target control the Cache for Oracle DB ? Since have allocated around 42GB for that?
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sdstuberCommented:
memory_target controls the upper bounds of the sga and pga

the sga contains the shared pool (cache of parsed queries and result cache of functions and queries) and buffer cache (cache of read blocks)

so yes -  but,  it is not the same thing as the OS cache
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GulfITAuthor Commented:
So in other wards Free Zero memory does not signify a problem.

Memory issues pops up only when the Swap starts to right to it?
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sdstuberCommented:
>>> So in other wards Free Zero memory does not signify a problem.

Not if there is more memory in cache

>>> Memory issues pops up only when the Swap starts to right to it?

Most likely.  If you are over-consuming memory but haven't swapped yet, then you might not notice the problem.
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GulfITAuthor Commented:
great.
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