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Need advice on below output

Posted on 2012-08-28
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Last Modified: 2013-02-11
Hi experts,

on the server dpt we have 11 db running currently... However we have plan of adding 4 more DB's ... below output shows there no Mem (free 748) left in the server ... However, if you seen -/+ buffers/cache free is 28GB free what is that? give me some light on it.

Whether i can create 4 more DB's ? what is the -/+ buffers/cache free is 28GB? how to flush?


oracle@dpt ~]$ free -m
             total       used       free     shared    buffers     cached
Mem:         32233      31485        748          0        547      27088
-/+ buffers/cache:       3849      28384
Swap:        18433       2098      16335

[oracle@Wdpt ~]$ top
top - 10:30:48 up 50 days, 11:48,  9 users,  load average: 0.82, 0.68, 0.76
Tasks: 669 total,   4 running, 663 sleeping,   0 stopped,   2 zombie
Cpu(s): 31.2%us, 18.8%sy,  0.0%ni, 43.8%id,  0.0%wa,  0.0%hi,  6.2%si,  0.0%st
Mem:  33007212k total, 32215900k used,   791312k free,   561160k buffers
Swap: 18876332k total,  2148836k used, 16727496k free, 27738328k cached


sk.
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Question by:Maddy
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12 Comments
 
LVL 20

Expert Comment

by:simon3270
ID: 38343097
Linux uses as much free memory as it can for input/output buffers and cache. If a program needs that memory, linux will relinquish it.

So, there is no need to "flush" buffers and
cache - memory will be available for any programs which need it.

However, you 11 DBs have used
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Expert Comment

by:simon3270
ID: 38343112
(oops, pressed enter too early)

Your 11 DBs have used 30GB, and you only have 2GB left. That may not be enough for 4 more DBs. You have plenty of spare CPU power.
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Expert Comment

by:jlevie
ID: 38343120
Unless there is an application on the system that has a memory leak, the only way to free up more memory would be to would be to stop an application. But that doesn't mean that you can't add more databases. Some memory will be recovered from that used for buffers  and more swapping will occur, both of which will affect performance.
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Accepted Solution

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Duncan Roe earned 600 total points
ID: 38343565
You have almost 27GB cached out of 32GB, which is very healthy.
On the other hand, you have almost 2GB of swap used. This may only indicate that the cached pages are being used more frequently than the paged-out written-to (dirty) pages. (The dirty pages all belong to running programs - dirty file system pages are written back to the file system, never to swap).
On the basis of the above, I would expect some graceful degradation (which may not even be noticeable) on adding 4 more DBs
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Expert Comment

by:Duncan Roe
ID: 38343592
@sim3270 Hi mate, sorry I don't understand your post http:#a38343112 Your 11 DBs have used 30GB. How do you get that? Cheers ... Duncan
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Expert Comment

by:simon3270
ID: 38344769
@duncan_roe, I misread the top output (my own fault for trying to do it on a phone!) - I miscounted the digits in the "cached" value, and thought that free, buffers and cached only added up to 2 GB.  Your 27GB is correct.

I don't think that an extra 4 DBs will have any noticeable effect on CPU or memory - the cached pages may be very infrequently accessed.  I don't even think that 2GB swap is much to worry about.
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Expert Comment

by:Duncan Roe
ID: 38348312
Nor did I, really
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Author Comment

by:Maddy
ID: 38830073
I've requested that this question be deleted for the following reason:

I'm Not found solution usefull..
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Expert Comment

by:Duncan Roe
ID: 38830074
Both responding experts said the asker had no problem and should go ahead with installing the extra DBs. We don't know what the he did because he never posted back.
I think the Q was fully answered.
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Expert Comment

by:Duncan Roe
ID: 38861549
I recommend to accept http:#a38343565. The Asker requested advice as to how to interpret the output from free and this advice was given.
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Expert Comment

by:simon3270
ID: 38863195
I agree with Duncan - the specified comment answered the question clearly and correctly.
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Author Comment

by:Maddy
ID: 38875032
Dear duncan_roe & simon3270,

Apologies. Its my mistake. Duncan answered correctly. I like to give point to Duncan... Thanks  again.
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