guys, sorry to say .. but now i am thoroughly confused - i have done something for which the link seems to work .. i am pasting what i had done -
i checked the sqlnet.ora of the other server and saw that default_domnin = tcskolkata.co.in
so i let the default_domain in my box to be tcskolkata.co.in

then as per reydp's suggestion .. i changed the tnsnames connect-desc riptor to pdsource.world

then according to akhadar i changed the global_name of both the databases to pdsource (but here the domain that got appended was different)

then i recreated the database link - which seemed to work fine.
this i executed from [email protected]d

SQL> select * from uii.ar_classes@pdsource_uii;

DEP COURSE
--- ----------
DESCRIPTION
------------------------------------------------------------------------------

MAX_STUDENTS CURRENT_STUDENTS NUM_CREDITS ROOM_ID CREDITS_ALLOWED
------------ ---------------- ----------- ---------- ---------------
PHY 1
OPTICS
100 75 9 100 9

BUT INTERESTINGLY IN THE OEM THE DATABASE LINK STILL TELLS ME NOT ACTIVE.

hey guys, can u give me a good info regarding these things -
when i am creating a link between 2 databases how does global_name, global_names, domain come into the picture and play a part

thanks and regards