"The fsync() blocks the process until all the dirty pages are written to
the physical disks" - maybe this is a problem with async i/o ?
How many async i/o servers are configured on the AIX box (use "smitty aio"
to check). As a start point set to the maximum to Number of CPU's * 10 and
set the min to half the max.
Just a thought...
Ade
-----Original Message-----
Sent: Wednesday, July 10, 2002 8:49 PM
To: LazyDBA.com Discussion
After migration from Oracle ver 7.3.4 to 8.1.7.2 (32-bit) , %wio (%iowait)
on Database Machine Exceedingly High i.e. about 60 % .
NOTE - This is a Live Production Site .
AIX 4.3.3
Storage Box = SSA Class Storage (7133-D40 Model)
Machine S85 P-Series
Application - Banking (Hybrid)
SAMPLE Output Below %iowait = 60.5 % - (Detailed Output file Attached )
tty: tin tout avg-cpu: % user % sys % idle %
iowait
1.2 10.0 8.9 21.8 8.9 60.5
Disks: % tm_act Kbps tps Kb_read Kb_wrtn
hdisk0 0.7 4.0 0.8 0 240
hdisk1 1.1 5.8 1.0 12 336
hdisk3 0.0 0.0 0.0 0 0
hdisk9 0.0 0.0 0.0 0 0
hdisk6 0.0 0.0 0.0 0 0
hdisk2 1.0 4.0 0.8 0 240
hdisk4 0.0 0.0 0.0 0 0
hdisk5 0.0 0.0 0.0 0 0
hdisk11 80.4 449.1 66.6 22292 4656
hdisk7 91.0 964.4 145.9 37868 19996
hdisk10 65.5 491.5 78.4 22916 6576
hdisk13 95.5 914.3 127.2 25656 29200
hdisk14 93.5 869.1 129.5 22824 29320
hdisk15 97.9 960.8 152.6 35620 22028
hdisk16 98.4 1382.8 174.7 53112 29856
hdisk8 75.0 802.9 119.4 40816 7360
cd0 0.0 0.0 0.0 0 0
----------------------------------------------------------------------------
--------
COMMENTS of Hardware Engineer :-
===============================
>From the perfpmr data collected on July 5th and it has
been analysed by our Labs.
The performance degradation is caused by fsync() routines called by Oracle
processes.
In 5 secs trace, fsync was called 276 times and consumed 21.39% CPU system
time.
The fsync() blocks the process until all the dirty pages are written to
the physical disks.
We checked the old perfpmr data collected with Oracle 7.3.4.5, it
doesn't have this issue.
Oracle has a fix to address the fsync problem on 8.1.7.2 (64-Bit) & 8.1.7.4
(32-Bit).
----------------------------------------------------------------------------
---------
WE HAVE INITIATED WITH ORACLE CORP FOR A PATCH ON 8.1.7.2 32-BIT.
Nevertheless Any Other Ideas just in case the Patch Does NOT bring Down the
%wio
Enough ?
NOTE - High %wio has been Observed only on AIX O.S. (NOT Other O.S.) post
migration
to Oracle 8.1.7.2
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