Create authentication alias in Websphere Application Server

I was recently involved in setting up the infrastructure for deploying web applications into Websphere App Server(WAS) v6.1. As a "weblogic bee", this is was something new to me. But over all, the experience was really great.

The tasks involved in the whole process is given below:
1) Installation of WAS6.1
2) Creating profile called appProfile using Profile Management Tool (in weblogic we create "domains" using domain config wizard)
3) Started the profile
4) Created connection pools, data sources
5) Resource reference mapping.
6) Implement custom user registry.
7) Deploy Web applications.
8) Map security role to user/group mapping.

After doing all of the above tasks, application would not connect to Data base using data source connection. It was throwing exceptions in the logs. It took couple of days to figure it out Websphere needs user name/password while creating connection. So login credentials can be passed

a) programmatically but this is a bad idea as hard coding user id/password in the application code.
b) create authentication alias mapping to a user name/password in websphere admin console

So this alias name must be mapped while creating data source itself..

ooooph! Finally it worked.

P.S: 
If you don't create an alias while establishing connection using data source in Websphere 6.1 you may end up getting this error below: 
Authentication Alias Websphere JNDI Data source Exception Connection Failed SQLException null userid is not supported. errorcode 4461