Hi, perhaps this might help you:
Cause of your problem:
Some datafiles are offline.
ORACLE instance terminated. Disconnection forced so this might cause the datafiles to be offlined
Solution:
Check if you have a good backup from which you can restore any problematic data file.
1) first restore the problematic datafile.
2) mount the database
SQL > recover database;
And then try to open the database
SQL > alter database open ;
3) Try to find if there are any offline files by checking the recover_file.
SQL> select * from v$recover_file;
For example:-
11 OFFLINE OFFLINE
2489793132
30-JAN-09
20 OFFLINE OFFLINE
2489793132
4) Recover the offline datafiles that were appearing from above select statement,
i.e.
SQL> recover datafile 11,20;
Media recovery complete.
5) Bring these datafiles back online,
i.e
SQL> alter database datafile 11,20 online;
Database altered.
6) To ensure no more files just check again the recover_file view, then you can safely open the database
SQL> select * from v$recover_file;
no rows selected
Hope this helps.