Re: database links and performance
- From: tboss@xxxxxxxxxxxxxxxxxx
- To: jknight@xxxxxxxxxxxxxx
- Date: Tue, 8 Feb 2005 11:36:39 -0500 (EST)
Selects from a dblink are "ok" performance-wise ... we've donesome rudimentary
benchmarking and seen very slight performance hits by including dblink'ed tables
in joins. Doing any sort of insert/update/delete over a dblink will be
a huge performance hit.
We've also seen bugs when using dblink'd tables in applications. You cannot
get query rewrite to work on any MV built on a base table located over
a dblink. (which kinda defeats the purpose of MVs in the first place).
boss
>
> I can second Tom's comment that "bad things happen" when joining across
> links. Especially if the remote tables have much size. Other strategies
> are create a function on the remote DB to return just a small result set
> across the link (if applicable.) Replicate certain data to your local DB
> depending on needs/space.
> We have also observed a performance hit (significant in some cases) even
> when both DBs are on the the same box. That said, links are a great thing.
> We use them all the time.
>
> Jon Knight
> Senior Database Analyst
> 2525 Horizon Lake Drive, Suite 120
> Memphis, TN 38133
> JKnight@xxxxxxxxxxxxxx
> 901.371.8000 - Phone
> 800.238.7675 - Phone
> 901.380.8336 - Fax
> www.FirstData.com
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