Re: LGWR blocking sessions

From: Fuad Arshad <fuadar_at_yahoo.com>
Date: Thu, 11 Jun 2009 14:06:10 -0700 (PDT)
Message-ID: <522840.73629.qm_at_web82102.mail.mud.yahoo.com>


I've had this issue and it seems to be 2 things. This happens in peak times i.e when the application is generating an archivelog a sec type deal. it seems lgwr is not able to catch up. there is a parameter that helps / The second thing is we started noticing this after we enabled dataguard.

note 34592.1 gives you some pointers to start looking at

  • Original Message ---- From: "Joel.Patterson_at_crowley.com" <Joel.Patterson_at_crowley.com> To: oracle-l_at_freelists.org Sent: Thursday, June 11, 2009 2:40:36 PM Subject: LGWR blocking sessions

My log writer is triggering an alert from OEM that it is blocking sessions. (SID ### is blocking -- which is LGWR).

I have googled, and searched metalink, and come across log file sync's, and even Kevin Closson's interesting blog about io and cpu (again :)).

Even though I can find people (several) with the same issue and question, I did not come up with any solutions that where directed specifically.

10.2.0.4, peoplesoft, SAN. Sidenote. Archiver is copying logfiles to a Quantum dxi7500, (with compression and deduping software bundled).

Any ideas where to go from here? (I'll be back early tomorrow)

Alert log snippet during time receiving two such alerts which looks normal. No trace files. Some db's have been know to warn of the 500ms write threshold was exceeded, but not here now.

Thu Jun 11 11:04:57 2009
Beginning log switch checkpoint up to RBA [0x1bc1.2.10], SCN: 2847388841 Thu Jun 11 11:04:57 2009
Thread 1 advanced to log sequence 7105 (LGWR switch)   Current log# 1 seq# 7105 mem# 0: /u02/oradata/HRPROD/log01a.log   Current log# 1 seq# 7105 mem# 1: /u03/oradata/HRPROD/log01b.log Thu Jun 11 11:10:02 2009
Completed checkpoint up to RBA [0x1bc1.2.10], SCN: 2847388841 Thu Jun 11 12:11:53 2009
Beginning log switch checkpoint up to RBA [0x1bc2.2.10], SCN: 2847490018 Thu Jun 11 12:11:53 2009
Thread 1 advanced to log sequence 7106 (LGWR switch)   Current log# 2 seq# 7106 mem# 0: /u02/oradata/HRPROD/log02a.log   Current log# 2 seq# 7106 mem# 1: /u03/oradata/HRPROD/l0g02b.log Thu Jun 11 12:17:11 2009
Completed checkpoint up to RBA [0x1bc2.2.10], SCN: 2847490018 Thu Jun 11 13:07:20 2009
Beginning log switch checkpoint up to RBA [0x1bc3.2.10], SCN: 2847597436 Thu Jun 11 13:07:20 2009
Thread 1 advanced to log sequence 7107 (LGWR switch)   Current log# 3 seq# 7107 mem# 0: /u02/oradata/HRPROD/log03a.log   Current log# 3 seq# 7107 mem# 1: /u03/oradata/HRPROD/log03b.log Thu Jun 11 13:12:36 2009
Completed checkpoint up to RBA [0x1bc3.2.10], SCN: 2847597436

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http://www.freelists.org/webpage/oracle-l Received on Thu Jun 11 2009 - 16:06:10 CDT

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