Syntax options:

       CONSTRAINT_MODE=IMMEDIATE
       CONSTRAINT_MODE=DEFERRED
       CONSTRAINT_MODE=ON
       CONSTRAINT_MODE=OFF

    You can optionally specify either the CONSTRAINT_MODE=IMMEDIATE
    or CONSTRAINT_MODE=DEFERRED qualifier on the SQL module language
    command line to set the default constraint evaluation mode for
    commit-time constraints. (This qualifier does not affect the
    evaluation of verb-time constraints.) The default is DEFERRED;
    that is, commit-time constraints are evaluated at commit time.

    Setting constraints ON causes each of the affected constraints
    to be evaluated immediately, as well as at the end of each
    statement, until the SET ALL CONSTRAINTS OFF statement is issued
    or until the transaction completes with a commit or rollback
    operation.

    The SET ALL CONSTRAINTS statement overrides the CONSTRAINT_
    MODE=IMMEDIATE or the CONSTRAINT_MODE=DEFERRED qualifier.

    SQL users who require ANSI-standard SQL compatibility should set
    constraints IMMEDIATE. The default (CONSTRAINT_MODE=DEFERRED) is
    acceptable for most other users.

    You can use the ON keyword instead of IMMEDIATE and the OFF
    keyword instead of DEFERRED.