RAC Re: Global Cache Null to X wait event..

  • From: "K Gopalakrishnan" <kaygopal@xxxxxxxxx>
  • To: racdba@xxxxxxxxxxxxx
  • Date: Wed, 23 Apr 2008 07:20:52 -0700


NULL-X is a wait during the new lock/block acquisition and there will
be numerous messages sent/received between the master and requestor
(and may be holder if your cluster is 3node and above). When you use
the public network for messaging traffic, you will not only exaggerate
the waits for NULL-X wait, but also the waits for ALL GC related work.

Do you care to share the  statspack/AWR?


On Wed, Apr 23, 2008 at 6:59 AM, Dubovecky, Jeffrey P
<jpdubovecky@xxxxxxxxxx> wrote:
> RAC DBA's,
> I'm running into an issue with a Global Cache Null to X wait event that
> we've found during an LTOM trace.  It seems that the issue in question is
> that we're inserting records into a block and deleteing different records
> from the same block, or at least that's how it appears from the LTOM trace.
> We also know we have interconnect issues, as the interconnect is on a public
> network and not on a private network.  This wait event happens a few times
> during the day, however it can take a PL/SQL routine up to 20 seconds to
> complete and is not specific to a specific PL/SQL routine that may
> insert/delete records from the same set of tables.  So here are my
> questions:
> 1.  Could the interconnect being on a public network exaggerate the Global
> Cache Null to X wait event?
> 2.  Besides rewriting the application to perform the delete at a later
> timeframe, what other suggestions can be implemented to reduce this wait
> event.
> Thanks for any assistance you can provide me in advance - JPD
> Jeff Dubovecky
> Consulting Engineer
> Union Switch & Signal
> 1000 Technology Drive
> Pittsburgh, PA  15219-3120
> Ph: 412-688-2881
> Fax: 412-688-2399
> Email:  jpdubovecky@xxxxxxxxxx

Best Regards,
K Gopalakrishnan
Co-Author: Oracle Wait Interface, Oracle Press 2004

Author: Oracle Database 10g RAC Handbook, Oracle Press 2006

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