Re: Old Chestnut: Tablespace Fragmentation

Bill,

I believe in that case your query will spend most time on data transfer and the percent of seeking time will be tiny provided that number of extents is reasonable. One thing to note: sizes of extents should be multiple of db_file_multiblock_read_count in order to minimize number of I/O operations required for FTS.

Regards,
Ed

>
>
> I know this one has been done to death: use uniform extents to avoid
> fragmentation; multiple extents don't hurt (within limits).
>
> But what if:
>
> Data Warehouse, one big table on a single disk, full table (batch) scan, no
> concurrent transactions on the database (so no contention for the disk), no
> fragmentation at the file system level, initially empty buffer cache
> (startup), read-only operation so DBWR isn't doing anything on this
> disk. Basically I want to read one data file from end to end. Surely it
> would make sense to have the disk read moving smoothly from one end of the
> disk to the other rather than bouncing about all over the place as it may
> do with multiple extents "randomly" allocated.
>
> Any thoughts?
>
> Thanks
> - Bill.
>
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> Author: Bill Buchan
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Edward Shevtsov
  INET: ed.shevtsov_at_mail.ru

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