3 statements only 3rd works - Is this not impossible?

Question

Hi there,
We have an overnight process which essentially does this
1. Updates a single row in table A
2. Inserts a single row into table A
3. Calls a procedure that creates multiple rows in table B
4. COMMIT
This process runs once a month and has failed to complete the last 2 months.
The odd thing is step 3 has partially worked and been commited to the database.
There is only one instance of the job that calls the procedure and we have audit records that confirm that step 3 ran when planned.
Is there any way that Oracle can think that steps 1 & 2 are successfully complete when they are not?
The only thing that has changed recently is that the client has moved the database data files onto a storage array network which has already caused some performance issues as the disk read times have been very slow.
Any thoughts?

Answer 1

Thanks for all the suggestions.
I am in the process of re-writing the event handling as it seems to be a 'bag of spanners'
The 3 steps are within an anonymous block within a procedure and have a single WHEN-OTHERS THEN RAISE statement.
We do have an automonous transaction based process log but the WHEN-OTHERS exception handlers don't use it! That as you can guess is about to change.
The frustrating thing is that we have not been able to reproduce the error when running through debug with a copy of the live database as it was when the job failed.
All I can do I guess is improve the error handling and 'hope' that it fails again.
It didn't fail this month and all we changed was the time the process ran by 30 mins after some other jobs.