Vladimir,

Do not forget that low hit ratio does not absolutely mean that you need to
increase your SGA.
Many site recommend other approaches that reach your tuning goals in a much
more efficient way.
If you can say that your database will run faster after any memory increase
than increase it otherwise ask your self why so many blocks are hit and if
it is in proportion with the data you get at the application client side.

look at svmon -G in the man pages.
Pay attention to file page memory and work page memory. The SGA is work page
memory but the files are probably also cached at OS level as file page
memory unless you use raw devices as direct IO is not used by Oracle on AIX.



You can raise the file / work pages cached in the memory by adapting the
minperm and maxperm values with the vmtune command. All this is well
explained in the online AIX documentation. The values recommended in the 101
oracle Performance book is 15 % and 50 % respectively.

If you decrease those values it will give you more place for work page
memory which the SGA is part of.


Jean Remacle

-----Original Message-----
From: Vladimir Polonsky [mailto:[Email Address Removed] mercredi 31 juillet 2002 9:20
To: LazyDBA.com Discussion
Subject: AIX command for free memory



Hi all,

My Oracle 8 is located at AIX machine. The db hit ratio is too low and I
want ot increase the db_block_buffers init value.

Question: how do I know how much free memory my AIX machine has?

Thank you all in advance,



Best regards,

Vladimir Polonsky




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