ORA-00600: internal error code, arguments: [kcratr_nab_less_than_odr]

It is for instance crash for power failure/instance aborted.
so control file has been corrupted.

So solution is :-
======================

[Before trying any kind of recovery, cold backup the entire database first]


1) SQL> conn / as sysdba

2) SQL> shutdown immediate ;

3) SQL> startup mount ;

4) SQL>

SELECT a.MEMBER, a.group#, b.status
FROM v$logfile a, v$log b
WHERE a.group# = b.group# AND b.status = 'CURRENT'

5) SQL> shutdown abort ;

6) SQL> startup mount ;

7) SQL> recover database using backup controlfile until cancel ;

Enter location(a.MEMBER) of redo log what found by 4) number point.
if it is not in archivelog mode. if it is in archivelog mode please enter the asking archivelog location. then press enter

it will show.......
Log applied.
Media recovery complete.

8) SQL> Alter database open resetlogs ;

9) Take hot backup of the database immediate.