[dba-SQLServer] SQL Server Book

Two instances of SQL Server, means that you have  two separate installations od the 
database engine running concurrently on the same machine 

The first time you instal SQL Server on a machine, it is automatically installed as  the "Default 
Instance".   You can then do a complete  instal  of SQL Server again, this time as a "Named 
Instance"  where you specify a different name and different port(s) for it to operate on.

The concept was introduces with SQL Server 2000.

See http://msdn.microsoft.com/en-us/library/aa174516%28v=sql.80%29.aspx

-- 
Stuart

On 19 Aug 2011 at 22:03, Alan Lawhon wrote:

> 
> What has me confused now is another section of the book where I read
> that you can have "two instances" of SQL Server running simultaneously
> on the same machine.  If I recalled correctly, that would seem to
> imply that an "instance" is a copy!  (Maybe what that sentence was
> implying is that you can have SQL Server running two different
> [application] databases off the same SQL Server database engine
> simultaneously - so the two separate databases are the "instances" -
> while the [installed] SQL Server database engine is the entity.)
> 
>