How to show the message text for constraint violations

Question

Hi all,
In a batch procedure a primary key is violated (ORA-00001). For the primary key, a message is recorded in the TAPI and the message table.
How to show the enduser a proper message text instead of the ORA-00001.
We are using Designer 6 with Headstart 2.1.2.
Thanks in advance,
Joep

Answer 1

Joep,
If you try to insert the record by calling the ins procedure of the Table API, you will see that it will result in an ORA-20998 message, which means that the error message details reside in the CG$ERRORS plsql message table. These messages can be extracted e.g. with the messages.sql script, shipped with headstart.
If you do not want to rewrite your direct DML (insert into [table name] ...) in the complexer calls to the TAPI services, you might want to user VAPI's for it. In fact, this is one of the major advantages of using VAPI's.
The CDM guidelines volume, chapter 6 states that:
<I>The front end no longer needs to trap declarative constraint
errors (Primary Key, Unique Key, Not Null and Check
Constraint violations) and replace them with a user-friendly
error. The View API issues DML statements through the TAPI
and the TAPI traps all declarative constraint errors, and puts
user-friendly message on the stack, in the preferred language of
the user! Fore more information, see the section, Completeness
of Rule Violations Reported in Front End, in this chapter.</I>
So the only thing you need to do is generate VAPI's, and trap the ORA-20998 message (qms$errors.qms$exception) in an exception handler, where you retrieve the user friendly messages from the message stack!!
Regards, Marc