Home » RDBMS Server » Performance Tuning » DBA_WAITERS , BLOCKERS $ V$LOCK (Oracle Enterprise Edition 10.2.0.4, Solaris 10)
DBA_WAITERS , BLOCKERS $ V$LOCK [message #476660] Fri, 24 September 2010 07:25 Go to next message
jesuisantony
Messages: 166
Registered: July 2006
Location: Chennai
Senior Member
Hi,

Can you let me know the difference in using DBA_WAITERS, DBA_BLOCKERS and using V$LOCK?

While querying V$LOCK, I am able to see the holding session and the blocking session. But whereas, DBA_WAITERS and BLOCKERS row count is always zero.

Please calrify on this.


Regards,
Antony

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Re: DBA_WAITERS , BLOCKERS $ V$LOCK [message #476684 is a reply to message #476660] Fri, 24 September 2010 09:26 Go to previous messageGo to next message
Michel Cadot
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Registered: March 2007
Location: Saint-Maur, France, https...
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These DBA views are written upon v$lock restricting the output to the sessions that wait on enqueue lock or block these ones.

Regards
Michel

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Re: DBA_WAITERS , BLOCKERS $ V$LOCK [message #476693 is a reply to message #476684] Fri, 24 September 2010 10:27 Go to previous messageGo to next message
jesuisantony
Messages: 166
Registered: July 2006
Location: Chennai
Senior Member
Does it mean, that we cannot rely on the DBA views always?

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Re: DBA_WAITERS , BLOCKERS $ V$LOCK [message #476695 is a reply to message #476693] Fri, 24 September 2010 10:40 Go to previous messageGo to next message
Michel Cadot
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No, this means they have a purpose and they serve this purpose.

As it is said in Database Reference:
DBA_BLOCKERS displays a session if it is not waiting for a locked object but is holding a lock on an object for which another session is waiting.
DBA_WAITERS shows all the sessions that are waiting for a lock. ("lock" here means an "enqueue lock" as it is its main meaning.)

Regards
Michel

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Re: DBA_WAITERS , BLOCKERS $ V$LOCK [message #477133 is a reply to message #476695] Tue, 28 September 2010 23:59 Go to previous messageGo to next message
jesuisantony
Messages: 166
Registered: July 2006
Location: Chennai
Senior Member
I have another query.

I understand that value of block, if it is 1= block. 2 means it is a global lock in an RAC. I went through some documents but unable to understand. In our environment (RAC), most of the block values are 2.

Not sure, if we can ignore it. Or is it something we need to do about it? Can some please explain me with examples?

Regards,
Antony

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Re: DBA_WAITERS , BLOCKERS $ V$LOCK [message #477135 is a reply to message #477133] Wed, 29 September 2010 00:05 Go to previous message
Michel Cadot
Messages: 68716
Registered: March 2007
Location: Saint-Maur, France, https...
Senior Member
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Quote:
I have another query.

Create a new topic with the appropriate title in the appropriate forum.

Regards
Michel

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