The SQL Server setup program sets permissions on the system tables in a database so that all database users can read the system tables.
However, the default is that no users – including database owners – can modify the system tables directly with SQL statements. Rather, the graphical tools (such as SQL Enterprise Manager) or system procedures are used to modify the system tables. (The SA can change this situation so that ad hoc modifications to the system tables are allowed. For more information, see Chapter 3, Configuring Servers.)
Important Never update the system tables unless instructed to do so by Microsoft technical support personnel.