Using XADatasource or non-XA Datasource for JTA based transactionsn in JPA

Question

We are using JPA 1.0 for ORM based operations and we want to have JTA datasource for our application. We are having only 1 database to which our application will connect. We start our transaction boundary in controller class and it goes till DAO layer controller--> BOImpl--> DAO. In websphere application server admin console when I am defining datasource should I use non-XA datasource or XA-Datasource.

My understanding is that for single datasource I should not use XADatasource. Please let me know what should I need to use.

Answer 1

For a single resource (like a single DB) you indeed do not need an XA-datasource.

On the other hand, bear in mind that most JTA/JTS implementations actually recognize that there is only 1 resource participating in a transactions, so the overhead for XA would be minimal or none then. There can also be additional participants in the transactions that you might now not think about, like sending JMS messages.

But if you're really sure you only have 1 resource participating, you can safely go for non-XA.

Answer 2

I hope your doubt may be clear by now, but here is more information on that just in case.

The typical XA resources are databases, messaging queuing products such as JMS or WebSphere MQ, mainframe applications, ERP packages, or anything else that can be coordinated with the transaction manager. XA is used to coordinate what is commonly called a two-phase commit (2PC) transaction. The classic example of a 2PC transaction is when two different databases need to be updated atomically. Most people think of something like a bank that has one database for savings accounts and a different one for checking accounts. If a customer wants to transfer money between his checking and savings accounts, both databases have to participate in the transaction or the bank risks losing track of some money.

The problem is that most developers think, "Well, my application uses only one database, so I don't need to use XA on that database." This may not be true. The question that should be asked is, "Does the application require shared access to multiple resources that need to ensure the integrity of the transaction being performed?" For instance, does the application use Java 2 Connector Architecture adapters or the Java Message Service (JMS)? If the application needs to update the database and any of these other resources in the same transaction, then both the database and the other resource need to be treated as XA resources.