RE: Dude, Where's My Database?

From: Stig Hornuff <hornuff_at_hotmail.com>
Date: Wed, 19 Jul 2006 12:25:23 +0000
Message-ID: <BAY116-F918E7717DA1890BC3328FA1600@phx.gbl>

"Allocating" and "using" are 2 rather different word in a linux-box. When Oracle starts and allocated 4G of SGA, you will most likely not see must usage on the memory as the memory-pages are just reserved for the purpose.
You will see memory usage grow when the database starts working and the buffer cache gets filled as it is the writing to the memory which brings it into use - and thus visibly allocated.

My own little Oracle 9.2.0.6, configured with 400MB uses ~58MB on startup - including binary core image, which is 51MB. However - starting of a real database burner makes it utilize a total of ~500MB for all server procs and SGA. This happens quite fast.

My 10g uses ~70MB in startup regardless of SGA size. But when used...... wooo-haa....

/Stig

----Original Message Follows----

From: Charlotte Hammond <charlottejanehammond_at_yahoo.com> Reply-To: charlottejanehammond_at_yahoo.com To: oracle-l_at_freelists.org
Subject: Dude, Where's My Database?
Date: Tue, 18 Jul 2006 07:15:22 -0700 (PDT)

Hi All,

My database is configured to use approx. 4Gb of memory:

Connected to:
Oracle9i Release 9.2.0.6.0 - 64bit Production JServer Release 9.2.0.6.0 - Production

SQL> select *

2 from v$sga
3 /

NAME                      VALUE


-------------------- ----------

Fixed Size               748656
Variable Size         805306368
Database Buffers     3355443200
Redo Buffers            1323008

Yet, Linux is saying there's < 1Gb physical memory in use and no swap. Where is my database?

(Apologies for the formating)

top - 16:08:21 up 2:17, 4 users, load average: 0.12, 0.11, 0.04
Tasks: 102 total, 1 running, 101 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.4% us, 0.1% sy, 0.0% ni, 99.3% id, 0.2% wa, 0.0% hi, 0.0% si
Mem: 8169180k total, 906124k used, 7263056k free,

39152k buffers
Swap: 2031608k total, 0k used, 2031608k free,

742984k cached

The database has been up for 2 hours but is very lightly loaded. Linux version is:

Linux 2.6.9-34.0.1.ELsmp #1 SMP Wed May 17 16:59:36 EDT 2006 x86_64 x86_64 x86_64 GNU/Linux

Doesn't Oracle allocate the entire SGA at start-up (or is on a demand basis?) I'd always understood it to be the former, in which case why can't I see it in memory using top?

Thanks for any info

Charlotte

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http://www.freelists.org/webpage/oracle-l Received on Wed Jul 19 2006 - 07:25:23 CDT