Database Reference
In-Depth Information
18.7 Named versus Default Instances
SQL Server has introduced the capability to run multiple, independent copies of the
database server on a single Windows-based computer. Microsoft supports up to 16 copies
of SQL Server installed on a single computer.
Default Instance:
One can connect to the default instance of SQL Server (there
is only one per machine) by specifying only the server name when connecting via an
application program. In earlier versions, connection to the SQL Server was done this
way — the SQL Server instance was specified as the machine name on which SQL Server
was running. For instance, if the computer is named
BDServ
, then to connect to the
default instance, you would specify
DBServ
when prompted for the SQL Server name.
The program files install to the default path of
\MSSQL
. The service names for the actual
SQL Server services are as follows:
•
SQL Server:
MSSQLServer
•
SQL Server Agent:
SQLServerAgent
Named Instance:
A named instance of SQL Server is one that is named during setup.
When you want to connect to a named instance, you specify both the server name and
the instance name that was entered during setup. The services are created with unique
names as well:
•
SQL Server:
MSSQL$Instancename
•
SQL Server Agent:
SQLAgent$Instancename
Common Components:
Some common components are shared between
installations of SQL Server; they do not really belong to either the default or any of the
named instances that might have been installed on the computer. They include the SQL
Server tools, as well as system components such as MDAC 2.6. For more information on
these, please refer to the MS SQL Server product documentation.
18.8 Removing MS SQL Server
If, for some reason, you need to remove SQL Server, simply use Control Panel 's Add/
Remove Programs — just like any other application on your computer. Selecting this
option removes all files and Registry keys related to SQL Server, but does not remove
shared components that were installed, such as the MDAC components. Also, if this is not
the last instance of SQL Server to be removed, the tools will remain. When you remove
the last instance of SQL Server, the tools are also removed.
We need to address one important issue regarding upgrade from to SQL Server from
an earlier version of the software. If for instance, you desire to upgrade from SQL Server 6.5,
do not run the 6.5 setup program to remove the previous release of SQL Server; this can
damage your SQL Server installation. Microsoft provides a special uninstall program for
SQL Server 6.5; it is accessible via a shortcut in the Microsoft SQL Server Switch menu;
it is called
Uninstall SQL Server 6.x
.
