Hi Nupur,
As far as stateless session bean is concern there will no data interference between different bean instance,reason is your session bean doesn't remember the state.
In app server we have pool concep for Entity and Stateless session bean. But remember both pools are different
As far as Stateless Sesssion bean pool is concern,this pool got all the ready state bean instance and container can directly assoicate these instance with you EJBObject.
So you can configure this parameter,that is how many instances shd be created when you server is up.
Now the question comes if all instance are busy to fill the client request than what ?
So some container wait till the time any busy instance gets free but some container re-create bean instance (configurable).
hope that is is clear to you.
Cheers,
Sunil Dixit