Hi Bob,
Although I don't know what version of MSSQL, I'll assume a newer
version...:)
From the SSMS side, set up an extended event, (tracing, to translate) and
track down what the difference is. Identify plan migration due to links,
views and distributed query. From there, once identified, lock the plan on
the SQL Server side to ensure the most optimal plan.
https://docs.microsoft.com/en-us/sql/relational-databases/extended-events/extended-events?view=sql-server-2017
Kellyn
On Wed, Dec 26, 2018 at 10:47 AM Stauffer, Bob <RStauffer@xxxxxxxx> wrote:
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@xxxxxxxx
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