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DBA_WAITERS , BLOCKERS $ V$LOCK [message #476660]

Fri, 24 September 2010 07:25

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

Michel Cadot
Messages: 68647
Registered: March 2007
Location: Nanterre, France, http://...

Senior Member
Account Moderator

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

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

Michel Cadot
Messages: 68647
Registered: March 2007
Location: Nanterre, France, http://...

Senior Member
Account Moderator

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

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

Michel Cadot
Messages: 68647
Registered: March 2007
Location: Nanterre, France, http://...

Senior Member
Account Moderator

Quote:

I have another query.

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

Regards
Michel

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