[ [[NOT] DEFERRABLE] [INITIALLY { IMMEDIATE | DEFERRED }] | [INITIALLY { IMMEDIATE | DEFERRED }] [[NOT] DEFERRABLE] ] [ RELY | NORELY ] [using_index_clause] [ ENABLE | DISABLE ] [ VALIDATE | NOVALIDATE ] [exceptions_clause]
For information on the symbols and conventions of Backus-Naur Form (BNF) syntax, see Appendix A.