ORA-31636: session is already attached to job string for user string
Cause : The session executing the attach is already attached to the specified job.
Action - How to fix it : DBA Scripts :: www.high-oracle.com/scripts
Select a different job or create a new session.
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.