RE: High "log file sync" wait in HP-UX Benchmark ?

From: Mark W. Farnham <>
Date: Fri, 23 May 2008 06:58:40 -0400
Message-ID: <016501c8bcc3$f6f4c4a0$>

Your average wait is only 9 ms. Your log file parallel write average wait is only 2 ms (that is probably getting handled in raid 5 write cache, I hope you're comfortable with that BAARF.)  

I think you are referencing the earlier benchmark you did in January when the average waits were on the order of 10 times worse than that in average wait and much larger in number of log file sync waits. At that time you had an actual problem with the i/o configuration.  

Take a look at JL's post from that time frame and analyze the effects of aggregation on your current situation. Very likely if you look at any individual transaction's session, it is not waiting significantly, but many of them are waiting a small amount in parallel. The way Oracle counts those waits in aggregation distorts the %Total Call Time in your report. JL's post referenced some convenient tools from Tanel and noted you don't have to do anything very sophisticated to see if you're looking at materially inflated numbers for waits.  



From: [] On Behalf Of VIVEK_SHARMA
Sent: Wednesday, May 21, 2008 4:00 PM
Subject: High "log file sync" wait in HP-UX Benchmark ?  


During a Benchmark, High "log file sync" wait is observed for OLTP Transactions  

Qs 1 What is the Solaris "maxphys" equivalent parameter on HP-UX 11.31? .. Increasing this had helped.

Qs 2 Will moving the Online Redo logfiles from Mounted Filesystem to RAW Devices help? ... This had significantly helped in the Solaris case since Oracle was using pwrite() function call to write to redo logfiles on Mounted Filesystem , while another function call (forgot which) was used to write to redo logfiles after they were moved to RAW Devices.

Qs 3 Since the Entire Set of Hard Disks is on RAID 5, could this be a significant cause for High logfile sync wait?

NOTE - Storage Box = HP EVA 600 SAN Storage Box

RAID 5 setup using SAME thereby consuming all of the 24 Hard Disks in the Box  

Will provide Statspack Report as needed.  

Cheers & Thanks in Advance  





HP-UX 11.31

Application - Hybrid Banking Product  

SP Report:-

Top 5 Timed Events                                                    Avg
~~~~~~~~~~~~~~~~~~                                                   wait
Event                                            Waits    Time (s)   (ms)
  • ------------ ----------- ------
log file sync                                  178,131       1,659      9
CPU time                                                       972
log file parallel write                        140,197         240      2
cursor: pin S                                  888,008         147      0
db file sequential read                         43,218          77      2
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Received on Fri May 23 2008 - 05:58:40 CDT

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