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v$pgastat value [message #440863] Wed, 27 January 2010 09:29 Go to next message
jinga
Messages: 115
Registered: January 2003
Senior Member
When i do a select on v$pgastat i get the following output along with other parameter settings.

select * from v$pgastat
aggregate PGA target parameter	285212672	bytes


but when i do

SELECT * from v$parameter where name like '%pga%';

we get 600M as the pga_aggregate_target.

My question is isnt aggregate PGA target parameter value should be the same as the one you see in v$parameter table for pga_aggregate_target. why would it be a different value?

Re: v$pgastat value [message #440864 is a reply to message #440863] Wed, 27 January 2010 09:38 Go to previous messageGo to next message
BlackSwan
Messages: 24905
Registered: January 2009
Senior Member
They are the same for me.

SQL> show parameter pga

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
pga_aggregate_target		     big integer 89M
SQL> select round(value/(1024*1024)) from v$pgastat where name = 'aggregate PGA target parameter';

ROUND(VALUE/(1024*1024))
------------------------
		      89
Re: v$pgastat value [message #440866 is a reply to message #440863] Wed, 27 January 2010 10:03 Go to previous messageGo to next message
Michel Cadot
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Registered: March 2007
Location: Nanterre, France, http://...
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1/ Do you set memory_max_target?
2/ Did someone execute alter system on pga_aggregate_target parameter?

Regards
Michel
Re: v$pgastat value [message #440868 is a reply to message #440863] Wed, 27 January 2010 10:39 Go to previous messageGo to next message
jinga
Messages: 115
Registered: January 2003
Senior Member


yes


SQL> show parameter memory_max_target

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
memory_max_target                    big integer 3G



Yes. memory_max_target is set like above.

It is possible that other dba might have executed.

alter system on pga_aggregate_target parameter

but what would be the performance implications because of the difference between v$pgastat value and v$parameter value. is there any?

Re: v$pgastat value [message #440870 is a reply to message #440868] Wed, 27 January 2010 11:05 Go to previous message
Michel Cadot
Messages: 63802
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
Quote:
but what would be the performance implications because of the difference between v$pgastat value and v$parameter value. is there any?

None.

If you set actual memory_max_target then pga_aggregate_target is under automatic memory management (see the line "aggregate PGA auto target").
Both reasons I mentioned can explain what you see.

Regards
Michel
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