Database administration involves a wide variety of activities. For example, the database management system can be used to set up a security system involving user accounts, passwords, permissions, and limits for processing the database. To provide database security, a user must sign on using a valid user account before she can process the database. In addition to security, DBMS administrative functions include backing up database data, adding structures to improve the performance of database applications, removing data that are no longer wanted or needed, and similar tasks. For important databases, most organizations dedicate one or more employees to the role of database administration.