Hi Vish Kumar,
The concept of SessionSynchronization interface is there because it gives a stateful bean a chance to synchronize itself with any persistent data that it deals with.
For example if a stateful session bean has a persistent field, then inside afterBegin() it will be appropriate to load the current value from the database.
afterCompletion() should be used to store the persistent field, if the transaction was comitted sucessfully.
Thanx
RUF
SCJP