Oracle Database Discussions

Hi,
thanks for reading this.
The problem is as follows:
I (software developer with experience in PL/SQL but only a little in administration) have a PHP based web page which calls the DB (stored Procedure). I have no control over timeout settings of PHP/Web server and the called stored procedure runs for an indeterminate amount of time.
In order to avoid web timeouts my solution would be for the web to call a stored procedure which creates (or enables?) a job, returns and monitors the job progress until it completes.

First question: Is this the right approach or are there preferable alternatives?

There is a seemingly endless number of web pages which list/explain the commands of the DBMS_Scheduler package and the syntax, but I have not been able to find a good tutorial which illuminates the conepts behind job queues, job classes, programs (how is it different from a stored procedure), windows and chains (if indeed these are all concepts connected with jobs).

One particular problem I have is figuring out how to handle the jobs (one-off or reuse, for example), since the frequency of use depends on the web user and it is therefor possible that one process is started before previous ones have finished.

If anyone knows of a good web page for this or can outline the workflow and objects involved, your help is much appreciated.
Thanks again,
Markus Schneider