shmmax vs. SGA

From: Miller, Jay <JayMiller_at_tdwaterhouse.com>
Date: Tue, 29 May 2001 09:15:22 -0700
Message-ID: <F001.00311FD7.20010529083551@fatcity.com>

Hi all,

We had gotten some extra memory for our production server and I was trying to increase our buffer cache again (I was leery of doing it all at once so I just doubled it the first time). I got a ORA-27123: unable to attach to shared memory segment with my first try (it worked after I reduced the buffer cache a bit) and I'm trying to figure out why.

Total memory on the machine is 4Gig.

shmmax=2048000000 (2000M)

4K Block size

I was able to start the database with a db_block_buffers of 350000 but not of 400000.

Current SGA:

NAME                      VALUE
-------------------- ----------
Fixed Size                47296
Variable Size         248659968
Database Buffers     1433600000
Redo Buffers            1040384

This gives a total of 1605M which should leave 295M still available. An extra 50000 blocks is only 195M. Is there something other than the total in v$sga that counts towards the shmmax? I can't find anything in my Oracle8 & Unix Performance Tuning book.

Thanks for any guidance!

Jay Miller
--

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--

Author: Miller, Jay
  INET: JayMiller_at_TDWaterhouse.com

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