Maintaining Integrity Constraints
After integrity constraints have been created, it often becomes necessary to change their state, or to otherwise manipulate them. This section covers those functions.
Enabling Constraints
A disabled constraint can be enabled in either of two ways: ENABLE NOVALIDATE or ENABLE VALIDATE.
ENABLE NOVALIDATE
For primary keys and unique constraints that already have existing indexes built on them, enabling a constraint NOVALIDATE is faster than enabling it VALIDATE because existing data is not checked for constraint violation. If this option is used, no locks are required on the table, and the option is therefore highly appropriate for OLTP environments where a lot of DML activity is taking place on the table.
The following ...
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