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

SQL>Startup mount ;

SQL>Show parameter control_files

Query 1
------------

sql>select a.member,a.group#,b.status from v$logfile a ,v$log b where a.group#=b.group# and b.status='CURRENT'

Note down the name of the redo log

SQL>Shutdown abort ;

Take a OS Level back of the controlfile (This is to ensure we have a backup of current state of controlfile)

SQL>Startup mount ;

SQL>recover database using backup controlfile until cancel ;

Enter location of redo log shown as current in Query 1 when prompted for recovery

Hit Enter

SQL>Alter database open resetlogs ;