Oracle in a Nutshell

Triggers

A trigger is a program that executes in response to a change in table data or to certain events that occur in the database. There is a predefined set of events that can be “hooked” with a trigger, enabling you to integrate your own processing with that of the database. A triggering event fires, or executes, the trigger.

Triggers are enabled on creation (via a CREATE TRIGGER statement) and can be disabled (so they do not fire) via an ALTER TRIGGER or ALTER TABLE statement:

ALTER TRIGGER trigger_name {ENABLE | DISABLE};

ALTER TABLE table_name {ENABLE | DISABLE} ALL 
   TRIGGERS;

Triggers cannot be created on SYS-owned objects.