RE: enq HW - contention waits
- From: Yong Huang <yong321@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Sat, 19 Apr 2008 15:35:08 -0700 (PDT)
Ravi,
Ric's suggestion is great. Before doing that, you can also try
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).
Is your tablespace ASSM? If not, consider moving the LOB segment to an ASSM
tablespace because it's more difficult to create HW contention on ASSM.
Yong Huang
> Subject: RE: enq HW - contention waits
> Date: Fri, 18 Apr 2008 17:41:06 -0500
> From: "Ric Van Dyke" <ric.van.dyke@xxxxxxxxxx>
>
> When I've run into this in the past the culprit was a table with a LOB
> and the extent size was way too small. For them many times when they
> hit the HWM they were also allocating more extents. In their case the
> entire system was hanging when this happened because it was a very high
> use table. The table was rebuild with a 256M extent size and they
> didn't have the problem.
>
> Find table (or other type of segment) that is extending frequently and
> that might be the issue. You're still going to hit the HWM every now
> and then, but hopefully you won't be extending the segment at the same
> time.
>
> -----------------------
> Ric Van Dyke
> Hotsos Enterprises
>
>
>
> > We have a production database running on RAC (4-node) (10.2.0.3 on
> > Solaris 10) and I'm noticing a lot of waits on "enq: HW - contention".
> > Doing a bit of researching tells me that it is related to HWM extensions
> > (concurrent inserts). We have no control on the application so I wonder
> > what could be done from the database end to tune this up (if anything).
> > Here's what I see from the AWR during the time it showed up --
> >
> > ...
> >
> > TIA,
> > - Ravi Gaur
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