jwcolby
jwcolby at colbyconsulting.com
Fri Aug 19 23:14:26 CDT 2011
My understanding is that the instances are actual services, the SQL Server service is running twice. Any instance can be running many different databases simultaneously. But what do I know? ;) John W. Colby www.ColbyConsulting.com On 8/19/2011 11:03 PM, Alan Lawhon wrote: > I plunked down a little over $50 today and bought a copy of "murach's SQL > Server 2008 for developers" book. This is a 750 page tome (including a > couple of Appendixes) that include instructions for downloading SQL Server > Express (with Tools), the Management Studio, Books Online and two sample > databases. There are 22 chapters in this book with heavy emphasis on T-SQL, > so I think this will be a very good study resource and prep guide for > passing the SQL Server Developer's exam - (i.e. 70-433). > > > > In scanning this book prior to purchase, I noticed that each chapter ends > with a section of "Terms" that were covered in the chapter. For instance, I > have seen frequent references to the term "instance" in Books Online, but > I've never been sure exactly what "instance" (or an "instance") means. > Based on what I'm reading in this book, an entity is a class of objects (for > instance "cars") and a particular car would be a member of that class, so if > a table represents a class of objects, then a row within the table would be > an instance. (An instance is not a copy - it's a member of a class.) > That's where I was getting confused - I thought "instance" was a copy, but > apparently it's not. > > > > 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.) > > > > Hopefully this book will help me unravel all the terminology and clear out > the cobwebs. > > > > Alan C. Lawhon > > > > _______________________________________________ > dba-SQLServer mailing list > dba-SQLServer at databaseadvisors.com > http://databaseadvisors.com/mailman/listinfo/dba-sqlserver > http://www.databaseadvisors.com > >