RE: lgwr/dbw0 did not issue pwrite64 sys call
Date: Sun, 27 Nov 2011 09:43:25 +0100
Message-ID: <4814386347E41145AAE79139EAA398981939EB82EE_at_ws03-exch07.iconos.be>
Chen,
During the time you traced the lgwr process, it has not written any data. Most time was spend with the read system call, followed by the semtimedop (semaphore operation). To know from where it is reading you would need to retrace the process without the -c flag and check which open call has returned the file descriptor you see in the read call. I think this can also be a memory structure (maybe reads from the redo log buffer). But I'm not very sure about this.
The note you referenced in your other mail puzzles me, as I always thought that all db processes are reading and writing directly to and from the database files and that asmlib is only responsible for the discovery and stamping of the asm disks.
I don't have an installation with asmlib to test myself, so could you trace a service process when it does some io (for example a large full table scan). Best is to trace the process directly after it has been started (certainly before the full table scan is started), so you see also the open calls for the datafiles (which will show you which flags are used).
Kind regards,
Freek D'Hooge
Uptime
Oracle Database Administrator
email: freek.dhooge_at_uptime.be
tel +32(0)3 451 23 82
http://www.uptime.be
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--- From: Sidney Chen [mailto:huanshengchen_at_gmail.com] Sent: zondag 27 november 2011 3:59 To: D'Hooge Freek Cc: oracle-l_at_freelists.org Subject: Re: lgwr/dbw0 did not issue pwrite64 sys call Freek, There is no AIO system call, io_submit and io_getevents. I wonder if there any way to identify which process is actually take care the Physical IO. oracle 16376 1 0 Nov14 ? 00:16:36 ora_lgwr_testsid $ strace -c -f -S time -p 16376 Process 16376 attached - interrupt to quit Process 16376 detached % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ----------------Received on Sun Nov 27 2011 - 02:43:25 CST
73.72 0.116262 222 523 read
20.97 0.033069 109 304 59 semtimedop
2.24 0.003530 14 260 kill
1.89 0.002981 2 1199 times
1.06 0.001674 8 203 semctl
0.04 0.000068 1 58 getrusage
0.03 0.000054 14 4 semop
0.02 0.000036 12 3 open
0.01 0.000009 9 1 sendmsg
0.00 0.000005 2 3 close
0.00 0.000003 1 4 rt_sigprocmask
0.00 0.000003 3 1 1 rt_sigreturn
0.00 0.000003 2 2 setitimer
------ ----------- ----------- --------- --------- ---------------- 100.00 0.157697 2565 60 total -- Regards Sidney Chen -- http://www.freelists.org/webpage/oracle-l