RE: ASH Buffer max size

  • From: "Milen Kulev" <makulev@xxxxxxx>
  • To: "'Martin Berger'" <martin.a.berger@xxxxxxxxx>
  • Date: Sat, 18 Apr 2009 20:51:29 +0200

Hello Martin,
it seems that the upper limit of _ash_size is 250MB (on 10g and 11g). I have
tested it on OEL5.3 with and (1CPU ;( only )
The parameter _ash_size is set as requested , but the real value of the
buffer is limited to 250MB
SQL>   select  POOL , NAME , BYTES   from  V$SGASTAT where NAME='ASH
buffers' ;

POOL         NAME                            BYTES
------------ -------------------------- ----------
shared pool  ASH buffers                 266338304

This result is independent of Oracle shared memory management discipline

HTH. Milen 

-----Original Message-----
From: Martin Berger [mailto:martin.a.berger@xxxxxxxxx] 
Sent: Donnerstag, 16. April 2009 21:25
To: makulev@xxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: ASH Buffer max size

Hi Milen,

a short google search brought some ambiguous informations:
it's controlled by _ash_size
one formula is
Max( Min ( No. of CPU * 2 M, 5% of SHARED_POOL_SIZE, 2% of  
another: max (min (#of CPUs * 2MB, 5% of SHARED_POOL_SIZE, 30MB), 1MB)  

both seem to be about 10g.

Currently I have no informations if there are any changes in 11g, sorry.

happy testing with _ash* parameters.


> Hallo Listers,
> I have s simple question:
> What is the maximum size if ASH buffers.
> Some documents say it is 30Mb, other documents say it is 128MB (for  
> 10GR2).
> Is there any change in the upper ASH buffers size 11GR1 ?
> Many thanks in advance.
> Best Regards. Milen
> --
> //


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