Oracle - Explain the factor that can cause the execution plan of a query to
change. posted by Babu
Kunwar
Explain the factor that can cause the execution plan of a query to change.
Execution plans are the steps that the database will go through while executing
queries. They are generated via the explain plan or set auto trace commands.
The execution plans can and do change as the underlying optimizer inputs
change. Execution plan can differ or change with respect to two factors:
Different Schema
Different Cost
Different Schemas can affect the Execution plan to change on the basis of the
following factors: Firstly if the execution and explain plan happen to be on
different databases. Secondly if two users differs in statement. For example
the user explaining the statement is different from the user running the
statement. Which means that two users might be pointing to different objects in
the same database, which results in different execution plans. Thirdly when
schema changes between the two operations.
Different Cost can also lead a user to change the execution plan.
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