SQL Guide : Using SQL for database administration : Managing user privileges and roles : Changing a password
  
Changing a password
You can change your password with the ALTER USER command. Administrators can also change passwords of other users.
Procedure
Use the following syntax to change the password of a given user:
ALTER USER username IDENTIFIED BY new_password
Example
The following statement changes the password of the user CALVIN to GUBBES
ALTER USER CALVIN IDENTIFIED BY GUBBES
Related tasks
Changing administrator’s user name and password
See also
Managing user privileges and roles