To change a trigger, you must either replace or re-create it. (The ALTER TRIGGER statement only enables, disables, compiles, or renames a trigger.)

To replace a trigger, use the CREATE TRIGGER statement with the OR REPLACE clause.

To re-create a trigger, first drop it with the DROP TRIGGER statement and then create it again with the CREATE TRIGGER statement.

To debug a trigger, you can use the facilities available for stored subprograms. For information about these facilities, see Oracle Database Development Guide.