Help for upgrading my hadoop-0.19.1 version to hadoop-0.20.2

[rajesh . p]

Hi,
   Currently i am running Hadoop-0.19.1.I want to migrate from  
Hadoop-0.19.1 version to Hadoop-0.20.2.Can any one suggest me how to  
go ahead.The main tasks are API migration and DFS migration.Thanks in  
advance.


Thanks & Regards
Rajesh Putta