 <p>1)If you forgot to disable speculative execution, It is possible that multiple instances of given Reducer could run, which would result extra data than expected into RDBMS. 2)Even we need the database driver for client machine, If you plan to connect to RDBMS from that client , it is not needed.</p> <p>So "1" option is correct.</p> <p>I got this solution , Can any body Improve this answer or let me correct If any issues. Thank you </p>