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A question about L-LOCK in DB2 DATA SHARING ENVIRONMENT.

 
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haohao

New User


Joined: 23 May 2008
Posts: 35
Location: beijing China

PostPosted: Wed Mar 24, 2010 12:24 pm    Post subject: A question about L-LOCK in DB2 DATA SHARING ENVIRONMENT.
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WHEN I RUN a bacth program with a plan bound with RELEASE(COMMIT),
a lot of time consumed in DB2 PARENT L-LOCKS ,PM reprot as below:

GLOBAL CONTENTION L-LOCKS AVERAGE TIME AV.EVENT
------------------------------------- ------------ --------
L-LOCKS 3:23.599428 268.4K
PARENT (DB,TS,TAB,PART) 2:47.167313 211.7K
CHILD (PAGE,ROW) 12.726702 19375.00
OTHER 23.705414 37292.00


WHEN I run it with plan bound with RELEASE(deallocate),the
PARENT lock almost disappear,but child lock increased about 50%:

GLOBAL CONTENTION L-LOCKS AVERAGE TIME AV.EVENT
------------------------------------- ------------ --------
L-LOCKS 27.246866 30499.00
PARENT (DB,TS,TAB,PART) 0.037746 49.00
CHILD (PAGE,ROW) 27.172850 30403.00
OTHER 0.036270 47.00


I am very confusing about that,why page level lock amount can be different in
that two mode. there is no X,S lock applid at tablespace or table level,
so the page level lock amout should be equal in that mode. correct me if
I was wrong,thanks in advance!![/quote]
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sushanth bobby

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Joined: 29 Jul 2008
Posts: 1013
Location: India

PostPosted: Wed Mar 24, 2010 10:46 pm    Post subject:
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HaoHao,

As per the basic defination,
COMMIT - Releases locks at next commit point
Deallocate - Releases the acquired locks only when the program terminates

Meaning, when deallocate is used all the locks in hold till the program terminates and thus the contention.

Can you tell us what your ACQUIRE value was ?

Thanks,
Sushanth
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haohao

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Joined: 23 May 2008
Posts: 35
Location: beijing China

PostPosted: Thu Mar 25, 2010 4:24 pm    Post subject:
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my PLAN BOUND WITH ACQUIRE(USE).

I think ACQUIRE and RELEASE only apply to parent lock,and child lock will always be released when commit is issued. SO,the child lock amout should be equal, becase the DML amount is equal .
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