Re: row cache lock contention parallel insert

I have done that already but still. But I just find out the possible cause after doing several tests.

The row cache is caused by space allocation when several PX slaves are inserting into several subpartitions, I noticed this after running two insert append, the first had tons of row cache waits and the second insert cero.

Looks like expected behaviour but in a 6 nodes RAC this look like a killer.

Thanks

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LSC


On Sat, Dec 19, 2009 at 7:01 PM, Greg Rahn <greg_at_structureddata.org> wrote:



> I dont recall the bug# but there is an issue related to quotas that

> can show when there are a relatively high number of concurrent PX

> sessions inserting into the same tablespace.  The work around is to do

> a direct grant (dba or unlimited quota sys priv is not sufficient).

> alter user <name> quota unlimited on <ts>;

>

> That may be enough for you to find the bug (look for the dc row cache

> stuff also).

>

> Hope that helps.

>

> On Fri, Dec 18, 2009 at 11:58 PM, LS Cheng <exriscer_at_gmail.com> wrote:

> >

> > The insert is simply insert append into... select, the degree of

> parallelism

> > is 8 for some tables, 4 for others and 2 for smaller tables. I can

> observe

> > that when there are 5 of these inserts running concurrently all of them

> > suffers high contention on row cache lock, specifically dc_object_ids and

> > dc_segments. Previously the load processes ran without parallel DML and

> > yesterday pdml was enabled. Same symptoms.

>

> --

> Regards,

> Greg Rahn

> http://structureddata.org

>


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