Optimizing loads from linked server

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Optimizing loads from linked server

hogpen

SSC Eights!

Points: 931
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October 18, 2013 at 3:37 pm

#299329

Hi, so I'm new to SQL Server and I recently started at a new job. We currently have about 50 jobs that run throughout the night that pull from a linked server and insert into our data warehouse.
Most of the jobs take a few minutes, but there are some that take several hours. The jobs are set up through SQL Agent as T-SQL jobs. We truncate the tables in our data warehouse daily and then load the records. Is there a more efficient way to do these loads in SSIS or a way to only load the changes that occur from the previous day?
Here's an example:
insert into dbo.claimdetail fields
select fields
from LinkedServer.prod1.dbo.clmdet
where exists (select * from LinkedServer.prod1.dbo.ClaimsToPull
where CN = cdclno and
WN = cdwkno)

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michael.ansaldi@gmail.com SSCommitted Points: 1701 More actions · Answer 1

I'd recommend using SSIS as its purpose is for developing ETL processes. If you want to stay within I would use a pass through approach via open query vs a distributed query like you're using. Meaning, send your statement to be executed on the remote server and have it pull the results back. Make sure that the remote server has proper indexing for the statement it's running.

insert into dbo.claimdetail fields

select fields

from LinkedServer.prod1.dbo.clmdet

where exists (select * from LinkedServer.prod1.dbo.ClaimsToPull

where CN = cdclno and

WN = cdwkno)

to

INSERT INTO claimdetail (col1,col2,...)

SELECT col1, col2, ....

FROM OPENQUERY (LinkedServer, 'SELECT col1, col2, ... FROM clmdet c WHERE EXISTS ( SELECT 1 FROM prod1.dbo.ClaimsToPull p WHERE c.Col = p.Col AND CN = CdClNo AND WN = CdWkNo')

Here is a great article from a MSDN blog:

http://blogs.msdn.com/b/sqlsakthi/archive/2011/05/09/best-performer-distributed-query-four-part-or-openquery-when-executing-linked-server-queries-in-sql-server.aspx

jonysuise Ten Centuries Points: 1206 More actions · Answer 2

Hi hogpen, and welcome to the forum 😀

Good thing would be also to drop non clustered indexes on your claimdetail table before ETL and recreates them after.

Hope it helps. 😎

Jonathan Bernardez Bernardez
___________________________________________________________
DBD. MCSA SQL Server 2012