SQL Server uses system databases to support different parts of the database management system (DBMS). Each database plays a specific role and stores information that SQL Server needs to do its job. The system databases are much like the user databases created in SQL Server. They store data in tables and contain the views, stored procedures, and other database objects that you also see in user databases. They also have associated database files (that is,
.ldf files) that are physically located on the SQL Server machine. Table 7.1 lists system databases and their related database filenames.