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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Freeable memory
Hi Mike,
I did a test on one of our 7.3 databases. It seems that some (but not all) freeable chunks get coalesced by flushing the shared pool. I tested it on a database with no other users logged in and took before/after pictures of the chunk breakdown.
SQL> select
ksmchcom contents,
count(*) chunks,
sum(decode(ksmchcls, 'recr', ksmchsiz)) recreatable,
sum(decode(ksmchcls, 'freeabl', ksmchsiz)) freeable,
sum(ksmchsiz) total
from
sys.x$ksmsp
where
ksmchcls not like 'R%'
group by
ksmchcom
/
CONTENTS CHUNKS RECREATABLE FREEABLE TOTAL
KGL handles 188 54776 54776
PL/SQL DIANA 72 6604 134196 140800 PL/SQL MPCODE 20 6496 25264 31760
PLS cca hp desc 1 164 164 PLS non-lib hp 1 2096 2096 character set m 5 21456 21456 dictionary cach 85 172468 172468 fixed allocatio 26 832 832 free memory 25 82956796 kzull 6 284 284
library cache 460 78924 67472 146396
multiblock rea 1 1040 1040 permanent memor 1 13179484 row cache lru 30 1320 1320 session param v 9 19764 19764
sql area 119 186336 149732 336068
16 rows selected.
SQL> alter system flush shared_pool;
System altered.
SQL> select
ksmchcom contents,
count(*) chunks,
sum(decode(ksmchcls, 'recr', ksmchsiz)) recreatable,
sum(decode(ksmchcls, 'freeabl', ksmchsiz)) freeable,
sum(ksmchsiz) total
from
sys.x$ksmsp
where
ksmchcls not like 'R%'
group by
ksmchcom
/
CONTENTS CHUNKS RECREATABLE FREEABLE TOTAL
KGL handles 67 19812 19812
PL/SQL DIANA 66 4508 125668 130176 PL/SQL MPCODE 12 3036 13648 16684
PLS cca hp desc 1 164 164 PLS non-lib hp 1 2096 2096 character set m 5 21456 21456 dictionary cach 78 144728 144728 fixed allocatio 26 832 832 free memory 35 83352232 kzull 6 284 284
library cache 164 27060 24940 52000
permanent memor 1 13179484 row cache lru 30 1320 1320 session param v 9 19764 19764 sql area 46 64152 60320 124472
15 rows selected.
SQL> As for determining the chunks per session, the only way I know is to dump the heaps via ORADEBUG DUMP commands. The trace files will have the breakdown of type and status for each chunk. I don't remember off the top of my head how to dump it for individual sessions but it can be researched. Here is a sample of ORADUBG DUMP HEAPDUMP 10:
HEAP DUMP heap name="sga heap" desc=0x8000001c
extent sz=0xfc4 alt=44 het=32767 rec=1 flg=2 opc=0
parent=0 owner=0 nex=0 xsz=0xc91a64
EXTENT 0
Chunk 85009b7c sz= 13179484 perm "perm " alo=7200716
EXTENT 1
Chunk 84009b80 sz= 15604404 free " "
Chunk 84eeb634 sz= 560 recreate "library cache " latch=0
ds 84eeb870 sz= 560
Chunk 84eeb864 sz= 96 freeable "library cache "
Chunk 84eeb8c4 sz= 172 recreate "KGL handles " latch=0
Chunk 84eeb970 sz= 288 recreate "KGL handles " latch=0
Chunk 84eeba90 sz= 560 recreate "library cache " latch=0
ds 84eebccc sz= 560
Chunk 84eebcc0 sz= 96 freeable "library cache "
Chunk 84eebd20 sz= 172 recreate "KGL handles " latch=0
Chunk 84eebdcc sz= 560 recreate "library cache " latch=856ca7e0
ds 84eec008 sz= 560
Chunk 84eebffc sz= 96 freeable "library cache "
Chunk 84eec05c sz= 3952 freeable "sql area " ds=84eee5e0
Chunk 84eecfcc sz= 296 recreate "KGL handles " latch=856ca7e0
Chunk 84eed0f4 sz= 168 recreate "library cache " latch=856ca7e0
ds 84eed330 sz= 168
Chunk 84eed19c sz= 392 freeable "library cache " ds=84eef190
Chunk 84eed324 sz= 96 freeable "library cache "
Chunk 84eed384 sz= 288 recreate "KGL handles " latch=0
Chunk 84eed4a4 sz= 4248 recreate "sql area " latch=856ca7e0
ds 84eee5e0 sz= 8200
84eec05c sz= 3952
Chunk 84eee53c sz= 560 recreate "library cache " latch=856ca7e0
ds 84eef190 sz= 952
84eed19c sz= 392
Chunk 84eee76c sz= 2496 freeable "sql area " ds=84efb478
Chunk 84eef12c sz= 88 free " "
Chunk 84eef184 sz= 96 freeable "library cache "
Chunk 84ef1638 sz= 1440 freeable "PL/SQL DIANA " ds=84ef4dfc
Chunk 84ef1bd8 sz= 96 freeable "library cache "
Chunk 84ef1c38 sz= 560 freeable "library cache " ds=84f8a988
Chunk 84ef1e68 sz= 2096 freeable "PL/SQL DIANA " ds=84ef4dfc
Chunk 84ef2698 sz= 2096 freeable "PL/SQL DIANA " ds=84ef4dfc
Chunk 84ef2ec8 sz= 2096 freeable "PL/SQL DIANA " ds=84ef9d70
Chunk 84ef36f8 sz= 2096 freeable "PL/SQL DIANA " ds=84ef9d70
Chunk 84ef3f28 sz= 1220 freeable "PL/SQL DIANA " ds=84ef9d70
Chunk 84ef43ec sz= 316 recreate "PL/SQL DIANA " latch=856ca898
ds 84ef4dfc sz= 8044
84ef0e08 sz= 2096
84ef1638 sz= 1440
84ef1e68 sz= 2096
84ef2698 sz= 2096
Chunk 84ef4528 sz= 44 freeable "library cache " ds=84ef6994
Chunk 84ef4554 sz= 216 recreate "PL/SQL MPCODE " latch=856ca898
ds 84f01008 sz= 2436
......... snipped .......
HTH Tony Aponte
Home SHopping network
-----Original Message-----
From: Michael Ghelli [mailto:mghelli_at_precise.com]
Sent: Wednesday, January 16, 2002 5:11 PM
To: Multiple recipients of list ORACLE-L
Subject: Freeable memory
All,
In trying to solve some Library Cache latch contention issues, I've been
stumped on the following issues:
1) Do freeable chunks get coalesced during an ALTER SYSTEM FLUSH
SHARED_POOL.
2) If freeable chunks are freed when a session disconnects, is there a way
to determine chunks per session? The idea here is better memory management
through better session management.
I've aleviated the majority of latch contention by altering the
_kgl_latch_count parameter, but haven't addressed what I think is the root
cause: an oversized shared pool. I've found scripts that show the amount of
memory occupied by the sql area and library cache, and most if the memory is
in freeable chunks. Before downsizing the shared pool, I'd like to have a
better understanding of how these chunks are managed.
Regards,
Mike G
-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Michael GhelliReceived on Fri Jan 18 2002 - 11:51:01 CST
INET: mghelli_at_precise.com
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