RE: Automatic Shared Memory question

  • From: "Allen, Brandon" <Brandon.Allen@xxxxxxxxxxx>
  • To: <tanel.poder.003@xxxxxxx>, "ORACLE-L" <oracle-l@xxxxxxxxxxxxx>
  • Date: Tue, 5 Sep 2006 09:47:03 -0700

Armed with the information provided by Tanel, I went back to my SR with
Oracle Support for more detail on "KGH: NO ACCESS" to see if I could get
them to corroborate what we're seeing and here is the answer I was

"KGH: NO ACCESS chunks are owned by the buffer cache and indicate a
partial transfer between buffer cache and shared pool."

I don't know why they couldn't tell me that the first time I asked - I
guess it was top-secret until Tanel blew it :)

So, this means that unless they change things - it will be very common
for sum(bytes) from v$sgastat to return a value significantly greater
than your sga_max_size, and the difference will probably be roughly
equal to the size consumed by "KGH: NO ACCESS".  This KGH: NO ACCESS
area should disappear completely after the instance is restarted - then
occasionally grow and shrink as granules are passed back and forth
between the shared pool and the buffer cache (if you are using Automatic
Shared Memory Management, e.g. sga_target > 0).


-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Tanel Poder
Sent: Tuesday, August 22, 2006 10:17 PM
Subject: RE: Automatic Shared Memory question

> I wonder if those buffers stored in the shared pool are being reported

> twice in v$sgastat - once under "KGH: NO ACCESS" and again under 
> "buffer_cache"?  That would explain why
> sum(bytes) from v$sgastat is so much larger than my sga_target & 
> sga_max_size.  I'll see if I can find a way to confirm this is what's 
> happening . . .

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