Re: enq HW - contention waits

From: Yong Huang <>
Date: Tue, 22 Apr 2008 08:08:12 -0700 (PDT)
Message-ID: <>


The key is the "instance X" option. Oracle documentation is not clear on this. The only thing I find at this time is in 8i OPS Admin Guide: "Unused space you have allocated to an instance using the ALLOCATE EXTENT command cannot be deallocated. This is because it exists below the high water mark."

I have a test done with a non-ASSM tablespace:

It may not apply if you use ASSM.

Yong Huang

  • Riyaj Shamsudeen <> wrote:

> Yong
> I must be missing something here. Just to clarify, are you saying that
> allocating an extent add space under HWM? Do you have any reference or test
> case?
> >> alter table theBLOBtable modify lob (theBLOBcolumn) (allocate extent
> (instance 1));
> >> Remember to include the "instance 1" so space is added below HWM, even if
> you're not using RAC (ignore documentation's caution: only use it on RAC).
> Thanks
> Riyaj Shamsudeen
> The Pythian Group
> On Sun, Apr 20, 2008 at 8:58 PM, Ravi Gaur <> wrote:
> > Yong, we already applied the patch 6376915 in Sep 07. We also use ASSM
> > still there are HW enqueue waits. I think the only other thing to try out
> > would be to preallocate extents to the LOB tables. Let me know if you've
> any
> > other ideas.
> >
> > Thank you.

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Received on Tue Apr 22 2008 - 10:08:12 CDT

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