Re: Monster Update

Matt wrote:

> I have an update statement which appears to be doing far more work
> than required.
>
> The following statement hits the disk repeatedly (via multiblock read)
> for an index fast full scan.
>
> UPDATE PS_TY_RECRUITMENT SET APP_DT = TO_DATE(SYSDATE,'YYYY-MM-DD')
> WHERE APPLID = 'A0021198' AND APP_DT =
> TO_DATE('2001-11-07','YYYY-MM-DD')
>
> The elapsed time is 30 seconds, of which over 17 seconds is spent
> waiting on multiblock I/O.
>
> The strange part is that when I run a query which should effectively
> perform the same lookup it returns instantly with no I/O wait
> occuring.
>
> This is the SQL which returns immediately:
>
> SELECT APP_DT FROM PS_TY_RECRUITMENT
> WHERE APPLID = 'A0021198' AND APP_DT =
> TO_DATE('2001-11-07','YYYY-MM-DD')
>
> Both statements perform an index FFS so why does the update take so
> much longer.....
>
> Any ideas would be greatly appreciated....
>
> Matt

Run explain plan and a trace ... find out what is different.

-- 
Daniel Morgan
http://www.outreach.washington.edu/ext/certificates/oad/oad_crs.asp
http://www.outreach.washington.edu/ext/certificates/aoa/aoa_crs.asp
damorgan_at_x.washington.edu
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