query from sql server linked server slow
Date: Wed, 26 Dec 2018 18:46:43 +0000
Message-ID: <e02c621c00ea4609858c8a4b9c3262e4_at_ASCEMAIL2.CENTRAL.FFCNETWORK.com>
Hi all,
Oracle 12.2, Red Hat 7, SQL Server 2012
I know, this isn't a SQL Server forum, but I'm running out of ideas on how to troubleshoot the following. When running a specific query from SQL Developer or SQLPlus on my Windows 7 PC in and Oracle database, that query is relatively fast. It returns 16 records in less than 20 seconds. But when run in a SQL Server instance using SSMS and using OPENQUERYlinked server, it never completes - it will actually run for days if we don't kill it. I've tracked it down to a difference in execution plans on the Oracle database side. Of course, when run in the Oracle database using SQL Developer, it generates an efficient execution plan. But when run via OPENQUERY/linked server in SQL Server, the execution plan in Oracle is horrendous. I've tried loading a better plan for the query using dbms_spm.alter_sql_plan_baseline, etc., but it ignores the new plan. And I've tried creating a view for the query, but that makes no difference either.
First, can anyone explain why 2 different execution plans are used in the Oracle db for the same query? Supposedly OPENQUERY/linked server are just submitting the query to Oracle for optimization without doing any "pre-optimization". And any thoughts on how I can troubleshoot/figure out how to fix or get around the problem?
Thanks much.
Bob Stauffer
rstauffer_at_fult.com
***CONFIDENTIALITY NOTICE***This email contains confidential information which may also be legally privileged and which is intended only for the use of the recipient(s) named above. If you are not the intended recipient, you are hereby notified that forwarding or copying of this email, or the taking of any action in reliance on its contents, may be strictly prohibited. If you have received this email in error, please notify us immediately by reply email and delete this message from your inbox. Thank you. E-Mail Opt Out Notice: This e-mail message may include an advertisement. You have the right to request that we not send future advertisements to you at this e-mail address. If you prefer not to receive future advertisements from us at this e-mail address, please access the following url http://www.optoutffc.com/ Fulton Financial Corporation, P.O. Box 4887, Lancaster, Pa. 17604
-- http://www.freelists.org/webpage/oracle-lReceived on Wed Dec 26 2018 - 19:46:43 CET