Triggers that are defined to trigger on DDL events for a specific schema or on DDL-related events for the database, are system triggers. These triggers can have detrimental effects on certain import operations. For example, they can prevent successful re-creation of database objects, such as tables. This causes errors to be returned that give no indication that a trigger caused the problem.
Database administrators and anyone creating system triggers should verify that such triggers do not prevent users from performing database operations for which they are authorized. To test a system trigger, take the following steps:
Define the trigger.
Create some database objects.
Export the objects in table or user mode.
Delete the objects.
Import the objects.
Verify that the objects have been successfully re-created.
A full export does not export triggers owned by schema
SYS. You must manually re-create
SYS triggers either before or after the full import. Oracle recommends that you re-create them after the import in case they define actions that would impede progress of the import.