1  –  DEFAULT

    The default constraint mode setting for a session is DEFERRED
    unless you have used one of the following to specify otherwise:

    o  SET DEFAULT CONSTRAINT MODE IMMEDIATE statement

    o  SQLOPTIONS=(CONSTRAINTS=IMMEDIATE) qualifier on the SQL
       precompiler command line

    o  CONSTRAINTS=IMMEDIATE qualifier on the SQL module language
       command line

2  –  constraint-evaluation-status

    Syntax options:

    OFF | DEFERRED

    This option causes constraint evaluation to be deferred until
    commit time, when the transaction completes. OFF is synonymous
    with DEFERRED.

3  –  IMMEDIATE

    Syntax:

    IMMEDIATE | ON

    This option causes constraint evaluation to be executed
    immediately, when the statement completes. ON is synonymous with
    IMMEDIATE.

    When you issue a SET ALL CONSTRAINTS IMMEDIATE statement, SQL:

    o  Evaluates all previously deferred constraints (those that
       would otherwise be evaluated at a COMMIT statement)

    o  Sets a mode in which SQL evaluates any constraints selected
       for deferred evaluation by the execution of an SQL statement
       at the end of that SQL statement (instead of waiting for a
       COMMIT statement)

    Once the transaction completes, the constraint mode is set back
    to the default constraint mode for subsequent statements.