Hello Mukesh,
I see you have had a lot of suggestions but what is being missed is that even if you resolve the problem in your "normal/active instance" (which you have done correctly) you are in the SHADOW nametab phase.
Cross check for shadow nametab tables to determine the correct table name and tablespace.
select owner, segment_name, tablespace_name from dba_segments where segment_name like 'DDNT%' and segment_type = 'TABLE' ;
Please post the output of the above command as I want to be 1000000% sure that the name of the shadow nametab tables hasn't changed before giving you further advice.
KR,
Amerjit