Oracle-L: RE: Cronjob

From: Sherman, Paul R. <PSherman_at_elcom.com>
Date: Fri, 10 May 2002 07:33:36 -0800
Message-ID: <F001.0045E3A8.20020510073336@fatcity.com>

Hello,

Has anyone ever tried setting dml_locks to zero or disabling table locks on an OPS (2-node, 8.1.7.2.1, 32-bit; HP 11.0, 64-bit) as a way of reducing contention and freeing up resources ? We currently use 7,250 dml_locks/instance. Oracle's OPS Admin manual (8i) had the following to say:

Obtaining table locks, such as DML locks, for inserts, deletes, and updates can
diminish performance in Oracle Parallel Server. Locking a table in Oracle Parallel
Server is undesirable because all instances holding locks on the table must release
those locks. Consider disabling these locks entirely using one of the two methods
described under the following headings:

Disabling Table Locks
Setting DML_LOCKS to Zero

We found, of our 200MB shared pool, that 108MB was taken up by State objects, gc_*, and dlm shared memory (100,000 gc_releasable_locks), frequently leaving us with just 3-6MB of shared pool free and getting occasional 4031's, so next week, plan on reducing the granularity considerably by setting gc_files_to_locks as 1=500R:2-600=100REACH, and gc_releasable_locks to roughly 30,000 (doing the math, you get 22,600 for the 1 system datafile and 221 other datafiles; we added 7,400 locks for 74 datafiles future growth). Adding up non-PCM and PCM locks would result in needing 120,123 for lm_ress and 180,185 for lm_locks.

Any assistance would be both informative and appreciated.

Thank you,

Paul Sherman
DBA Elcom, Inc.
voice - 781-501-4143 (direct #)
fax - 781-278-8341 (secure)
email - psherman_at_elcom.com
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Author: Sherman, Paul R.
INET: PSherman_at_elcom.com

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