Databases Reference
In-Depth Information
We are now satisfied with the execution plan obtained, and we want it to be the access path
for this query from now onwards. For this, we create a stored outline in step 4. Stored outlines
can be grouped together in categories, so we define
CUST_LIST_OUTLINE
to be part of the
APP_LISTS
category, where we will store all the outlines related to lists in our application.
There is no need to create a category before creating the outline—the category
APP_LISTS
doesn't already exist in our database, so it's created along with the stored outline, with a
single statement.
In step 5, we instruct the optimizer to use, for our session, the stored outlines of the
APP_LISTS
category. We can carry out the same operation also at a database level, affecting all the users
connected to the database instance. In the following screenshot, you can see the execution of
these statements:
In step 6, we execute the same query as in step 3, obtaining the same execution plan. The
execution plan will be the same even if we alter database parameters and/or the schema, for
example, adding an index. Our aim of plan stability is reached, as we can see in the following
screenshot (in the Note section):
