Database User Create/Alter

Create User:

SQL> CREATE USER <username>
IDENTIFIED BY <password>
DEFAULT TABLESPACE <tablespace name>
TEMPORARY TABLESPACE <tablespace name>
QUOTA <quota amount> ON <tablespace name>;

You then need to grant appropriate roles to the user for example, session, connect, resource:

SQL> grant connect,resource to <username>;

Change Password:

SQL> alter user <username> identified by <newpassword>;

Unlock User:

SQL> alter user <username> account unlock;