Oracle PL/SQL Programming, 5th Edition

Building an Effective Error Management Architecture

PL/SQL error raising and handling mechanisms are powerful and flexible, but they have some drawbacks that can present challenges to any development team that wants to implement a robust, consistent, informative architecture for error management.

Here are the some of the challenges you will encounter:

• The EXCEPTION is an odd kind of structure in PL/SQL. A variable declared to be EXCEPTION can only be raised and handled. It has at most two characteristics: an error code and an error message. You cannot pass an exception as an argument to a program; you cannot associate other attributes with an exception.

• It is very difficult to reuse exception-handling code. Directly related to the previous challenge is another fact: you cannot pass an exception as an argument; you end up cutting and pasting handler code, which is certainly not an optimal way to write programs.

• There is no formal way to specify which exceptions may be raised by a program. With Java on the other hand, this information becomes part of the specification of the program. The consequence is that you must look inside the program implementation to see what might be raised—or hope for the best.

• Oracle does not provide any way for you to organize and categorize your application-specific exceptions. It simply sets aside (for the most part) the 1,000 error codes between –20,999 and –20,000. You are left to manage those values.

Let’s figure out how we can best meet most of these challenges. ...