RE: High "log file sync" Waits in Statspack, - Online Redo Logs on Mounted File system of SAN Storage

From: <>
Date: Sat, 12 Jan 2008 00:29:32 -0700
Message-ID: <009a01c854ec$e1067150$6401a8c0@BHAIRAVIPC01>


<<< Qs How should this issue be approached? >>> 1. Presuming an OLTP system, you would be committing when the transaction is done. Nevertheless you should verify that you are committing in a manner that models the business transaction and not based on a, perhaps, contrived example.

2. You are trying to deal with the aggregate with this report. What part of the response time is the log file sync (commit) time? Take one of the threads of this benchmark and run a level 8 SQL trace to get a more accurate picture of its influence.

3. I would look at whether you are IO bound or so CPU bound that the LGWR is not getting time. And determine the time log writer to is made to write vs its default timer and thresholds.

Cary Millsap's work in Steve Adams' work in


Krish Hariharan
President/Executive Architect, Quasar Database Technologies, LLC  

-----Original Message-----

From: [] On Behalf Of VIVEK_SHARMA
Sent: Friday, January 11, 2008 6:57 PM
Subject: High "log file sync" Waits in Statspack, - Online Redo Logs on Mounted File system of SAN Storage


During a Benchmark Run of OLTP Transactions very High "log file sync" wait is occuring
Storage Box - Sun StoreEdge 9990V (Hitachi SAN) Online Redo logfiles exist on Mounted Filesystem on a LUN / Volume of 4+4 Hard Disks , (RAID 1+0 Type)
Hard Disk - 15 K RPM
Storage Cache - 128 GB
Online Redo Logfile size 750 MB
log_buffer= 4M

Solaris 10

Qs On the Storage Box, should a few of its HBA Controllers & respective Ports be assigned dedicatedly only to the online Redo LUN / Volume? Qs Should Online Redo Logiles be moved to RAW Devices on the SAN Storage? Qs Any advisable init.ora parameters?

Qs How should this issue be approached?

Will share Statspack as needed

Cheers & Thanks


Top 5 Timed Events                                                 Avg
~~~~~~~~~~~~~~~~~~                                                 wait
Event                                     Waits        Time (s)    (ms)
  • ------------ ----------- ------
log file sync                             3,511,274    328,288     93

SQL*Net break/reset to client 732,491 49,120 67 11.0

CPU time 31,699 7.1

latch: virtual circuit queues 1,099,453 10,695 10 2.4

db file parallel write                    3,253,478    9,535       3

Host CPU (CPUs: 80)

~~~~~~~~ Load Average

Begin End User System Idle WIO WCPU

  • ------- ------- ------- ------- ------- --------
                9.13    1.79

               16.35   23.30   60.35    0.00    2.79

Load Profile     Per Second Per  Transaction

~~~~~~~~~~~~     --------------- ---------------

Redo size:       3,143,457.88    4,121.10


Block changes: 15,320.88 20.09


Physical writes: 2,176.56 2.85

User calls: 14,769.89 19.36


Logons: 3.55 0.00

Executes: 12,950.32 16.98

Transactions: 762.77

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-- Received on Sat Jan 12 2008 - 01:29:32 CST

Original text of this message