Jonathan,
I believe it's to prevent other DBWR processes from
attempting to modify blocks belonging to the truncated
object until all of them have had a chance to flush
the blocks, but I honestly don't remember all the
details. I'll dig up my notes when I'm back in the
office and post them to the list.
- Anita
- Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
wrote:
> That's an interesting thought, but why do you
> think that only one DBWR process can scan
> at a time ?
>
> If you have multiple working data sets,
> surely you can have one dbwr process
> per working data set doing the scanning.
> After all, each working data set has its
> own 'range reuse' list (or should that be
> the 'object reuse' list for truncate)
>
>
> Jonathan Lewis
>
> Host to The Co-Operative Oracle Users' FAQ
> http://www.jlcomp.demon.co.uk/faq/ind_faq.html
>
> Author of:
> Practical Oracle 8i: Building Efficient Databases
> See http://www.jlcomp.demon.co.uk/book_rev.html
>
> For latest news of public appearances
> See http://www.jlcomp.demon.co.uk
>
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>
>
>
>
> -----Original Message-----
> To: Multiple recipients of list ORACLE-L
> <ORACLE-L_at_fatcity.com>
> Date: 18 August 2001 14:41
>
>
> |
> |The size of the buffer cache and the number of
> |DB_WRITER_PROCESSES has a big impact on the time it
> |takes to truncate a table.
> |
> |Each DBWR process has to scan its portion of the
> |buffer cache to flush any blocks belonging to the
> |truncated table or its indexes. This is a
> sequential
> |process as only one DBWR process can do this at a
> |time.
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Received on Sat Aug 18 2001 - 09:26:40 CDT
