RE: High "log file sync" Waits in Statspack, - Online Redo Logs on Mounted File system of SAN Storage
Date: Sat, 12 Jan 2008 14:09:35 +0530
Message-ID: <69E1360E54B50C4A828A136C158E4742036A707673@BLRKECMBX02.ad.infosys.com>
Thanks Richa, folks for the support & related Link(Kevin Closson's)
% System CPU usage is about DOUBLE of %User CPU usage:-
Qs What could be the possible cause?
NOTE - db_file_multi_block_read_count was NOT set by Oversight & defaulted to a value of 98. Could this be a probable cause?
Qs Should LGWR process be set to a Higher CPU priority(using renice) since 60% of the CPU power is FREE/Unused? NOTE - cpu_count=80
Solaris 10
From Statspack - NON-RAC setup (Oracle 10.2.0.3):-
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
Additional replies to your questions, are given below prefixed by "=>"
Cheers
From: richa03_at_gmail.com [richa03_at_gmail.com] Sent: Saturday, January 12, 2008 8:11 AM To: VIVEK_SHARMA
Subject: Re: High "log file sync" Waits in Statspack, - Online Redo Logs on Mounted File system of SAN Storage
Are you using asyncIO for DBWR?
disk_async_io=TRUE (Default)
How many sessions were active during the run?
10,000
How long was the run in wallclock time?
45 minutes
What is the priority of the Oracle processes?
=> Default [Higher priority (using renice) NOT set yet.]
Folks
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
Oracle 10.2.0.3
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
P.S.
Top 5 Timed Events Avg %Total ~~~~~~~~~~~~~~~~~~ wait Call Event Waits Time (s) (ms) Time ----------------------------------------- ------------ ----------- ------ ------ log file sync 3,511,274 328,288 93 73.6 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 2.1 -------------------------------------------------------------
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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