RE: DB Links

  • From: "Vergara, Michael (TEM)" <mvergara@xxxxxxxxxxx>
  • To: <klange@xxxxxxxxxx>, "Oracle-L (E-mail)" <oracle-l@xxxxxxxxxxxxx>
  • Date: Wed, 22 Sep 2004 15:14:05 -0700

Kevin:

I don't know the direct answer, but I found the same solution.
I had a query that did a join of two tables in a local database
and then inserted into a remote db table.  Sort of...

insert into table@remote
select a.col1, b.col1
from   tab1 a, tab2=20
where  a.col2 =3D b.col3

...and it took for-blinking-ever.  I created a global temporary
table, inserted into that, and then inserted from the GTEM
table to the remote table and processing dropped to mere moments.

It was a puzzlement to me because the work (ie: the join) I=20
presumed was being done on the local machine prior to the=20
insert to the remote table.  My fix was a late-night-oh-my-
doG-fix-the-problem solution and I never got the time to go
back and find the why.

Cheers,
Mike


-----Original Message-----
From: Kevin Lange [mailto:klange@xxxxxxxxxx]
Sent: Wednesday, September 22, 2004 2:44 PM
To: Oracle-L (E-mail)
Subject: DB Links


Does anyone happen to have a reasonable explaination on what happens to =
a
query when you try to access tables accross db_links ??  Does it still =
use
the indexes on the remote machine ??  Does it bring all the data locally
into temp tables ??

Any info will do.  Book names .... Actual explainations ... directions =
to
web sites ...   Anything.

We have a procedure, a fairly complex procedure, that takes about 13 =
hours
to run when it is ran against tables that exist accross a DB link.  But,
when we copy all the tables locally, it runs in about an hour.  We would
like to try and find a way to fix this.  But first, I need to know =
exactly
what is happening when the cursor access those linked tables.

Any help would be appreciated.

Kevin
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