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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Free Shared pool memory
Sorry for being so vague, but sometimes I can't help it...
It was my understanding in the Oracle7 days that the name of the statistic "free memory" was actually a verb and a noun (i.e. as in "free Nelson Mandela" or "free Willy"), and the number shown alongside this statistic was the cumulative number of bytes freed in the Shared Pool. In other words, every time "N" bytes were freed from the Shared Pool, then the statistic was incremented by "N". At least, this explanation would have accounted for the absurdly huge numbers seen in the V$SGASTAT view for this statistic in those versions and the unreliability in attempting to add the numbers seen in V$SGASTAT to sum to SHARED_POOL_SIZE...
Then, sometime in the Oracle8 or Oracle8i timeframe, the meaning of the statistic was changed so that the term "free memory" became what everyone had thought it was, an adjective and a noun (i.e. as in "free beer" or "free time"). A much more useful statistic, certainly...
Is this true? If not, is it close?
The sum of the information in V$SGASTAT still does not add to SHARED_POOL_SIZE, though (query from v8.1.7.4.0 shown below): SQL> select name, bytes from v$sgastat 2 where pool = 'shared pool';
NAME BYTES
-------------------------- ----------
free memory 18208352
miscellaneous 2378964
DML locks 120000
PLS non-lib hp 2096
trigger inform 944
PL/SQL MPCODE 1146204
PL/SQL DIANA 1223360
PX subheap 123476
db_block_hash_buckets 1411080
sessions 377300
KGK heap 48124
State objects 267420
message pool freequeue 124552
Checkpoint queue 885168
enqueue_resources 222912
db_files 370988
KGFF heap 649844
KQLS heap 1709904
dictionary cache 12670280
table definiti 3228
transactions 171264
ksfv subheap 4248
fixed allocation callback 1280
library cache 89490788
simulator trace entries 240000
sql area 187432036
table columns 19520
processes 123380
partitioning d 152976
db_block_buffers 10880000
event statistics per sess 607600
----------
sum 331067288
SQL> show parameter shared_pool_size
NAME TYPE VALUE ------------------- ------- ---------
I'm curious about the 16,494,488 bytes difference. Is it possible that V$SGASTAT is another "unlatched" data structure in memory, allowing errors in the interest of eliminating contention? There are other similar structures in the SGA (i.e. the data structure underlying table MONITORING statistics later flushed to SYS.TABMOD$)...
Thanks for any and all insight!
>
> I think it's safe to say that if the free memory is always very large
> then you can reinterpret it as 'wasted memory'.
>
> If the free memory is alway very small, I don't think it is possible
> to make any decision without know the application. It is possible
> that you need to increase the shared pool slightly (good app), it is
> also possible that your shared pool is just about the right size
> (great
> app) , but it is possible that your application design has a flaw in
> it.
>
>
> Regards
>
> Jonathan Lewis
> http://www.jlcomp.demon.co.uk
>
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>
>
> -----Original Message-----
> To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> Date: 02 January 2003 05:39
>
>
> >
> >Is it Correct to Look at FREE Memory in the Shared Pool ?
> >Memory when used once thereafter when NO Longer in use does the FREE
> Memory again Come up ?
> >Are there any ideal Values for percentage of Free memory for the
> Shared Pool
> >
> >The Respective Hybrid Application mostly uses Bind Variables
> >
> >Thanks
> >
> >
> >
> >--
> >Please see the official ORACLE-L FAQ: http://www.orafaq.net
> >--
> >Author: VIVEK_SHARMA
> > INET: VIVEK_SHARMA_at_infosys.com
> >
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> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Jonathan Lewis
> INET: jonathan_at_jlcomp.demon.co.uk
>
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-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Tim Gorman INET: Tim_at_SageLogix.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Thu Jan 02 2003 - 08:44:15 CST
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