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

  • From: VIVEK_SHARMA <VIVEK_SHARMA@xxxxxxxxxxx>
  • To: "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
  • Date: Sat, 12 Jan 2008 14:43:57 +0530

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@xxxxxxxxx [richa03@xxxxxxxxx]
Sent: Saturday, January 12, 2008 8:11 AM

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

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