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v$pgastat value [message #440863]

Wed, 27 January 2010 09:29

jinga
Messages: 116
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?

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Re: v$pgastat value [message #440864 is a reply to message #440863]

Wed, 27 January 2010 09:38

BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal

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

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Re: v$pgastat value [message #440866 is a reply to message #440863]

Wed, 27 January 2010 10:03

Michel Cadot
Messages: 68732
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

1/ Do you set memory_max_target?
2/ Did someone execute alter system on pga_aggregate_target parameter?

Regards
Michel

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Re: v$pgastat value [message #440868 is a reply to message #440863]

Wed, 27 January 2010 10:39

jinga
Messages: 116
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?

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Re: v$pgastat value [message #440870 is a reply to message #440868]

Wed, 27 January 2010 11:05

Michel Cadot
Messages: 68732
Registered: March 2007
Location: Saint-Maur, France, https...

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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