unable to connect to DB return code is 0012

hi team

please help while running SGEN due to power problem my laptop got shutdown when i checked after a restart it is not connecting to db

when i start up it is giving the below error

database already mounted

SQL> alter database open;

alter database open

*

ERROR at line 1:

ORA-00600: internal error code, arguments: [kcrfr_update_nab_2], [0x9DEF64CC],

[2], [], [], [], [], []

SQL>