Hi Vishal

I think the SID is not being exported properly..Pando is 100% right (as usual :-))

what shell are you using..after exporting the SID try testing it

env |grep ORACL_SID and see what is being shown on your terminal

in BASH and korn you export env variables something like this

export ORACLE_SID=newsid

in bourne shell u do soemthing like this
ORACLE_SID=newsid
export ORACLE_SID

regards
Hrishy