Re: LGWR blocking sessions

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@xxxxxxxxxxx" <Joel.Patterson@xxxxxxxxxxx>
To: oracle-l@xxxxxxxxxxxxx
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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