What is does a transaction monitor do?

[Anon]

For a project we are starting we want to select DB2 as our database. This IBM guy told us that we need to run a transaction monitor on our webserver(s) which ofcourse is part of the (expensive!) websphere application server. He told us that the transaction monitor checks whether a database transaction realy has succeeded from the webserver's point of view. If this is the correct explanation I'd like to know if php has built in support for such transaction monitor.

Regards,

Ronald van der Lee

[Anon]

Nope.

The current version of MySQL does not support transactions. I believe that PostgresSQL does, but I've never used that.

A transaction can be considered as a related set of database actions. This isn't a textbook definition, but it's good enough for a decent understanding.

Let's take a basic example of a simple sales / inventory database application. If a customer buys 10 widgets 5 frizzbots, you might want to:

1. Debit the customer's account
2. Reduce your inventory of widgets and frizzbots by 10 and 5
3. Generate an order for the required items

What if step 3 fails - the order can't be generated. It makes no sense to decrease the inventory if you can't create the order. Likewise, you don't want to debit your customer's account if you don't generate the order - you can't bill him for what you're not going to give him.

So, these 3 steps are an "all or nothing" set of actions. If they don't all happpen, then none of them should happen.

And that's what a transaction is.

mySQL doesn't know diddly about them by default, but if you have enough development time, you can reproduce some of the functionality by hand. Or you could just ditch mySQL and look at postregsSql.

Hope This Helps,

Jack