Thanks a lot Pradeep.
Need more information as i am doing upgrade first time. 
I search For upgrade Guide also but didnt get it on SDN.
what is backup strategy in case of NWDI, BPM ,WDJ,EJB and MDM component before doing upgrade?
As far i know Latest SCa file will contain all my web dynpro component ,EJB.
what is your thought if i upgrade CE 7.2 to CE 7.4? Please Suggest.
Also share your Experience about the efforts how much time it took for CE upgrade?
Thanks You
Aditi