When you compile a trigger at design time or generate a form module, the compiler detects any errors that would prevent the trigger from executing successfully at runtime. Other errors, however, manifest only at runtime, and are often impossible to avoid.
When a runtime error occurs, you need to detect and respond to the error in your trigger code so it does not interrupt the flow of the application. Triggers should be written to handle runtime errors gracefully, rather than allowing them to disrupt the work of the form operator.
Oracle Forms default functionality helps you handle runtime errors by detecting errors as they occur, issuing error messages, setting the values of error variables, and, when appropriate, rolling back transactions that cannot be completed successfully. You can supplement default error handling by writing triggers that respond to errors in an application-specific manner.
Note: This section assumes you are familiar with PL/SQL error handling techniques.
About using PL/SQL exception handling in triggers
About handling exceptions raised in triggers
About evaluating the success or failure of Built-ins
Handling errors in Built-in subprograms
Handling errors in user-named triggers