Facing problem in distributed queries over Oracle linked server

Question

Hi,
I have a SQL Server 2005 x64 Standard Edition SP3 instance. On the instance, we had distributed (4 part) queries over an Oracle linked server running fine just a few hours back but now they have starting taking too long. They seem to work fine when OPENQUERY
is used. Now I have a huge number of queries using the same mechanism and is not feasible for me to convert all queries to OPENQUERY, please help in getting this resolved.
Thanks in advance.

Answer 1

Hi Ashutosh,
According to your description, you face performance issues with distributed queries and
it is not feasible for you to convert all queries to
OPENQUERY. To improve the performance, you could follow the solutions below:
1. Make sure that you have a high-speed network between the local server and the linked server.
2. Use driving_site hint. The driving site hint forces query execution to be done at a different site than the initiating instance. 
This is done when the remote table is much larger than the local table and you want the work (join, sorting) done remotely to save the back-and-forth network traffic. In the following example, we use the driving_site hint to force the "work"
to be done on the site where the huge table resides:
select /*+DRIVING_SITE(h)*/
ename
from
tiny_table t,
huge_table@remote h
where
t.deptno = h.deptno;
3. Use views. For instance, you could create a view on the remote site referencing the tables and call the remote view via the local view as the following example.
create view local_cust as select * from cust@remote;
4. Use procedural code. In some rare occasions it can be more efficient to replace a distributed query by procedural code, such as a PL/SQL procedure or a precompiler program.
For more information about the process, please refer to the article:
http://www.dba-oracle.com/t_sql_dblink_performance.htm
Regards,
Michelle Li