Re: LOCK_SGA on HPUX
- From: Mladen Gogala <gogala@xxxxxxxxxxxxx>
- To: sjaffarhussain@xxxxxxxxx
- Date: Sun, 12 Dec 2004 10:40:49 +0000
On 12/12/2004 05:22:12 AM, Jaffar_DBA wrote:
> Friends,
>=20
> Any of you using LOCK_SGA parameter on HPUX 11.23 in the production?
> Are there any pros & cons, please share your valuable informtion.
Personally, I am not locking my SGA in memory. If you lock your entire =20
SGA in memory, then swapper cannot swap out parts of the SGA that are =20
not used and update daemon cannot steal unused SGA pages and throw them
out to disk. In other words, you are taking control of a large part of =20
your memory away from the virtual memory system. If there are many =20
processes accessing database and if you are using dedicated server (for =20
instance, if you want to take advantage of the automatic work are =20
sizing) the memory of your server is guaranteed to become extremely =20
busy. Frequently used pages will stay in memory because of the nature =20
of the virtual memory system which does its best to keep frequently =20
used things in memory. If there is a procedure locked in SGA by using =20
dbms_shared_pool.keep, which is used once, or twice during the course =20
of the day, then you don't necessarily want to keep pages containing =20
this procedure in memory and you can allow your VM system to page them =20
out and create a sort area for your busy DW users. In other words, your =20
VM system already does a good job with balancing your memory. You =20
should trust it.
--=20
Mladen Gogala
Oracle DBA
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