Oracle-L: RE: Block size written

From: Cary Millsap <cary.millsap_at_hotsos.com>
Date: Tue, 21 Oct 2003 07:34:31 -0800
Message-ID: <F001.005D3DE5.20031021073431@fatcity.com>

Lee,

Are you sure you're specifying the right process? When I use truss -p on my DBWR, it gives exactly what you need. In the following test, I used truss (strace on my Linux machine) to show what DBWR did in response to a "create table test as select * from dual; drop table test;" executed in another session:

09:25:31 $ ps -ef | grep dbw

oracle    1133     1  0 Oct09 ?        00:00:01 ora_dbw0_V901
cvm      12013 11962  0 09:29 pts/0    00:00:00 grep dbw

09:25:32 $ strace -p 1133 -e trace=write,pwrite --- SIGALRM (Alarm clock) ---
..
--- SIGALRM (Alarm clock) ---
pwrite(17, "\20\2\0\0\253\v@\0\244G\33\0\0\0\2\4\266#\0\0\0\0\0\0\0"..., 4096, 12234752) = 4096
--- SIGALRM (Alarm clock) ---
..
--- SIGALRM (Alarm clock) ---
09:27:09 $

By doing a "man pwrite", I can see the explanation of the pwrite return value of 4096:

RETURN VALUE

       On success,  the  number  of  bytes  read  or  written  is
       returned  (zero indicates that nothing was written, in the
       case of pwrite, or end of file, in the case of pread),  or
       -1  on  error,  in which case errno is set to indicate the
       error.

Therefore, my DBWR is writing 4,096 bytes at a time.

Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com

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-----Original Message-----
Robertson Lee - lerobe
Sent: Tuesday, October 21, 2003 9:34 AM
To: Multiple recipients of list ORACLE-L

Hi,

Oracle 9.2.0.3
AIX 5L Is there a way of finding the block sizes that are being written from the
database. We are experiencing write waits now, after solving our read issues.

We have looked at truss -p on AIX and it doesn`t seem to show this.

Regards

Lee

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Received on Tue Oct 21 2003 - 10:34:31 CDT