ORA-28026: user with same external name already exists
Cause : The external name specified for the user being created or altered already exists for another user.
Action - How to fix it : DBA Scripts :: www.high-oracle.com/scripts
External names must be unique among users. Specify another.
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.