Recognizing Roles

In multiuser RDBMSs, each database is controlled or owned by a specified user, charged with certain responsibilities, and bestowed with certain rights. These rights and responsibilities vary widely among database management systems, but they often include

• Setting up permissions for other users within the database

• Making backup copies of the database on a regular basis and running the recovery procedures in case of system failure

• Enlarging the database if more space becomes necessary

• Owning most of the production database objects

• Understanding the kind of data that is in the database and how it is used

In most database system installations, only the system administrator worries about physical storage. Users who issue the SQL commands to create databases or the objects in them (tables and views, for example) may do so according to instructions from the system administrator.

Depending on both the database software and the hardware you're using, databases may be physically stored on disks, on disk partitions, or in operating system files. We use the generic term database device for all of these possibilities.