If you want to delete a user account and its associated schema, you can log in as SYSTEM and use the DROP USER command as shown in the following example:

>.insqlplus /nolog

SQL> connect SYSTEM/globalguideline

Connected.

SQL> DROP USER DEV CASCADE;

User dropped.

SQL> CREATE USER DEV IDENTIFIED BY developer ACCOUNT UNLOCK;

User created.

Note that CASCADE tells the server drop the associated schema.