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Wait Stats [message #515393]

Mon, 11 July 2011 06:23

gxeon
Messages: 53
Registered: January 2011
Location: Mumbai

Member

Hello Sir

I am new to Oracle DBA , Need help.

When i running the fallowing query in production from v$waitstat view, i found the values as data block=3302, undo block=88, undo header=1725. from some online sites i got to know that to reduce the contention on data blocks we have to increase the DBWR process. Please let me know if there is another ways to reduce the data block values apart from increasing the DBWR process by adding 'db_writer_processes' parameter in my init file.

select CLASS,COUNT,TIME from v$waitstat order by CLASS;

please help

GG

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Re: Wait Stats [message #515399 is a reply to message #515393]

Mon, 11 July 2011 06:41

Michel Cadot
Messages: 68645
Registered: March 2007
Location: Nanterre, France, http://...

Senior Member
Account Moderator

Post what you see.
Anyway to get a performances view of your instances it is better to generate AWR or StatsPack report than to query v$waitsat.

Regards
Michel

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Re: Wait Stats [message #515722 is a reply to message #515399]

Wed, 13 July 2011 01:32

gxeon
Messages: 53
Registered: January 2011
Location: Mumbai

Member

Hello Sir

As an extend, from v$waitstate view we are getting the value for undo block=88 which shows the high contention rate.By some online blogs i found that by increasing the PCTFREE value of the tables being modified we can resolved the contention.

Is this the only way possible or there are some other ways to resolve this contention.

please help
I am new to Oracle DBA

Regards
GG

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Re: Wait Stats [message #515731 is a reply to message #515722]

Wed, 13 July 2011 02:31

Michel Cadot
Messages: 68645
Registered: March 2007
Location: Nanterre, France, http://...

Senior Member
Account Moderator

We don't see what you see, if you don't post it we can't help you.
And do what I said.

Regards
Michem

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Re: Wait Stats [message #515871 is a reply to message #515393]

Wed, 13 July 2011 22:24

hkchital
Messages: 128
Registered: September 2008
Location: Singapore

Senior Member

Those figures are *cumulative* wait counts since the database instance was started up. So, if the database instance was started only 60 minutes ago, 3300 and 1700 waits are a concern.
If the database was started up a few days ago, would you consider 3300 occurrences of wait in X days high ?

That is why StatsPack and AWR (if you have the Diagnostic Pack licence) come in hand. You can generate reports for intervals -- e.g. a report showing database activity, statistics and waits over a defined 1 hour. Then, you can consider if X waits in 1 hour is a high count.

Hemant K Chitale

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