Home » Oracle » 1z0-052 v.2 » Which action would you take to delay the referential integrity checking until the end of the transaction?
You have two tables with referential integrity enforced between them. You need to insert data to the child table first because it is going to be a long transaction and data for the parent table will be available in a later stage, which can be inserted as part of the same transaction.
View the Exhibit to examine the commands used to create tables.
Which action would you take to delay the referential integrity checking until the end of the transaction? Exhibit:
A. Set the constraint to deferred before starting the transaction
B. Alter the constraint to NOVALIDATE state before starting the transaction
C. Enable the resumable mode for the session before starting the transaction
D. Set the COMMIT_WAIT parameter to FORCE_WAIT for the session before starting the transaction
Correct Answer: A
Explanation/Reference:
Specifying Constraint State
As part of constraint definition, you can specify how and when Oracle should enforce the constraint. constraint_state You can use the constraint_state with both inline and out-of-line specification. You can specify the clauses of constraint_state in any order, but you can specify each clause only once.
DEFERRABLE Clause The DEFERRABLE and NOT DEFERRABLE parameters indicate whether or not, in subsequent transactions, constraint checking can be deferred until the end of the transaction using the SET CONSTRAINT(S) statement. If you omit this clause, then the default is NOT
DEFERRABLE.
Specify NOT DEFERRABLE to indicate that in subsequent transactions you cannot use the SET
CONSTRAINT[S] clause to defer checking of this constraint until the transaction is committed. The checking of a NOT DEFERRABLE constraint can never be deferred to the end of the transaction.
If you declare a new constraint NOT DEFERRABLE, then it must be valid at the time the CREATE TABLE or ALTER TABLE statement is committed or the statement will fail.
Specify DEFERRABLE to indicate that in subsequent transactions you can use the SET CONSTRAINT[S] clause to defer checking of this constraint until after the transaction is committed. This setting in effect lets you disable the constraint temporarily while making changes to the database that might violate the constraint until all the changes are complete.
You cannot alter the deferability of a constraint. That is, whether you specify either of these parameters, or make the constraint NOT DEFERRABLE implicitly by specifying neither of them, you cannot specify this clause in an ALTER TABLE statement. You must drop the constraint and re-create it.
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