Saving the State of a System

Question

A very flowery title indeed.

I have a PHP web application that is in the form of a web based wizard. A user can run through the wizard and select options, run process (DB queries) etc. They can go backwards and forwards and run process again and again.

I am trying to work out how to best save the state of what users do/did, what process they ran etc. So basically a glorified log that I can pull up later.

How do I save these states or sessions? One option which is being considered by my colleague is using an XML file for each session and to save everything there. My idea is to use a database table to do this.

There are pros and cons for each and I was hoping I could get answers on which option to go for? Suggestiosn of other options that are feasible would be great! Or what kind of questions should I ask myself to choose the right implementation.

Technologies Currently Used

Backend: PHP and MS SQL Server, running on Windows Server 2005

FrontEnd: HTML, CSS, JavaScript (JQuery)

Any help will be greatly appreciated.

EDIT

There will be only one/two/three users per site where this system will be launched. Each site will not be connected in any way. The system can have about 10 to 100 sessions per month.

Answer 1

Using a database is probably the way to go. Just create a simple table, that tracks actions by session id. Don't index anything, as you want inserting rows to be a low-cost operation (you can create a temp table, add indexes, and run reports on it later).

XML files could also work -- you'd want to write a separate file for each sessionid -- but doing analysis will probably be much more straightforward if you can leverage your database's featureset.

Answer 2

If you're talking about a large number of users doing there operations simultaneously, and you'd want to trace their steps, I think it's better to go for a database-oriented approach. The database server can optimize data flow and disk writes, leading to a better concurrent performance than constantly writing files on the disk. You really should try to stress-test the system, whichever you choose, to make sure performance does not suffer in the event of a big load.