Oracle error handling

Question

Hi, all
I'm new to Oracle and trying to find which Oracle predefined exceptions to handle explicityly in my sp/package. I'll need to do this to capture all available for specific action, then translate them into "User friednly" message to be sent to client without going into ORA-9999 details. I excpect to hard code most probable Exceptions and the rest hadnle with WHEN OTHER..
Also what the best way to keep ORA-9999 type messages for later review, is there any special logging mechanism for Oracle, so I can access them after execution.
Also I read that EXCEPTION should be coded at the end of the sql block, that bit confusing for me, is it alwayse it's the end of actual procedure ? or there is some type of "block" delimiter. In another words, can I write some other code after EXCEPTIONS?
For my case I'm looking for list of EXCEPTION for the following sql code:
for SELECT (to cursor):
for UPDATE:
Thansk
T

Answer 1

You will, of course, handle the exceptions you expect to see - like NO_DATA_FOUND, and other typical processing exceptions.
For the others, you have three choices
1. Let the exception bubble up to the user so that he can see that something really bad happened. When he opens a trouble ticket to report that something awful happened, he will pass the full text of the exception message ticket and you will have some idea of what happened and where in the code.
2. Capture the input arguments and processing steps along the way in the procedure and write them to a log - delete anything over three days old. Then when something bad happens place a marker entry into the log with the error stack, call stack. Now you can pass a message back to the user to say something like 'Something bad happened. Please contact application support.'.
3. Create a package to handle exceptions for you - this is a rather sophisticated piece of code - that will trap and log exception details and, possibly, create an entry in the alert log or trace file. You will call this from the exception handler, then return and pass a message back to the user telling him that something bad happened.
Some how or other, you will need the information provided by the error stack to help you identify the root cause and fix the problem.