Oracle-L: RE: High %wio on AIX O.S. DB Server after Oracle 8i Migration

From: Adrian Roe <Adrian.Roe_at_telewest.co.uk>
Date: Thu, 11 Jul 2002 06:08:23 -0800
Message-ID: <F001.00494CD7.20020711060823@fatcity.com>

"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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Author: Adrian Roe
  INET: Adrian.Roe_at_telewest.co.uk

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Received on Thu Jul 11 2002 - 09:08:23 CDT