fix for ORA-03113 end-of-file on communication channel:-
1. SQLPLUS / AS SYSDBA
2. startup mount;
SQL> alter database clear unarchived logfile group 1;
Database altered.
SQL> alter database clear unarchived logfile group 2;
Database altered.
SQL> alter database clear unarchived logfile group 3;
SQL> shut immediate;
SQL> startup ;
