SQL Server Execution Plans - Red Gate Software

Chapter 8: Advanced Topics
Aside from the procedure to create plan guides, a second one, sp_control_plan_
guide, allows you to drop, disable, or enable a specific plan guide; or drop, disable, or
enable all plan guides in the database.
Simply run execute the sp_control_plan_guide procedure, changing the @
operation parameter appropriately.
EXEC sp_control_plan_guide @operation = N'DROP',
@name = N'MyFourthPlanGuide'
Listing 8.19
Plan forcing
The USE PLAN query hint, introduced in SQL Server 2005, allows you to come as close
as you can to gaining total control over a query execution plan. This hint allows you to
take an execution plan, captured as XML, and store it "on the side," for example, inside a
plan guide, and then to use that plan on the query from that point forward. This doesn't
stop the optimizer from doing its job. You'll still get full optimization depending on the
query, but then whatever plan the optimizer produces is not used. Instead, it uses the
plan you're "forcing."
You cannot force a plan on:
• INSERT, UPDATE or DELETE queries
• queries that use cursors other than static and fast_forward
• distributed queries and full text queries.
Forcing a plan, just like all the other possible query hints, can result in poor performance.
Proper testing and due diligence must be observed prior to applying USE PLAN.
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