ORA-16099: internal error ORA-00600 occurred at standby database
Cause : The RFS process on the standby database received an internal error.
Action - How to fix it : DBA Scripts :: www.high-oracle.com/scripts
Check the standby alert log and RFS trace files for more information.
Well, the reason for above error is that i have taken the above script from a 11g database and running it on 10g database. 11g has bring some changes in password management. Below code is executed on 11g and user created successfully, which is expected result.