February 9, 2006 at 11:06 pm
I am seeking some clarification regarding the term "SQL Server Instance." The title SQL Server 2000 Unleashed goes like this:
"Regardless of whether the memory is allocated dynamically or is fixed, the total memory space for each SQL Server instance on a system is considered a single unified cache and is managed as a collection of various memory pools."
Could somebody clarify what we mean exactly by a SQL Server Instance? Is it a previous version of SQL Server installed on your computer? I am confused since the term "instance" has a very specific meaning in Oracle. I believe that is not the same meaninig in SQL Server. Please clarify.
Thanks,
Karim
February 10, 2006 at 12:14 am
In a nutshell,
treat an instance like a separate sql server system, in one box, you can have more than 1 instance depending on the version you have
you can actually have 2 versions of sql server system and you can refer these as 2 instances
HTH
February 10, 2006 at 6:45 am
Agree with Jen.
I heard that in Oracle Instance=Database
But in SQL it is Instance = SQL Server
http://www.windowsitpro.com/SQLServer/Article/ArticleID/8686/8686.html
"Microsoft didn't build in a hard limit for the maximum number of named instances you can install, so technically no limit exists. However, the SQL Server developers have tested the product with up to only 10 instances on one machine and have decided that 16 instances is the maximum that Microsoft will officially support."
February 10, 2006 at 8:45 am
When you install SQL Server on a computer for the first time, it installs as a Default instance (unless you name it). This instance has the Master, Model, MSDB, TempDb, and 'test' databases (for 2000, it's Northwind and Pubs). You can create user databases in this instance. You can then install SQL Server a second time on the same computer, without uninstalling the first install. This install will prompt you for a name, this creates a NAMED INSTANCE. Again, you will have Master, Model, MSDB, TempDB, the 'test' databases and you can create user databases in this instance also.
Why create different instances? Security for one thing. You could have an instance for Sales, one for HR, one for Management, and even one for testing.
One thing to remember with different instances...they are all separate SQL Server instances on the same computer. When you do a patch (service pack or hotfix) or upgrade...you MUST do it for each instance separately.
-SQLBill
February 13, 2006 at 4:27 am
One more logical reason of instance is as below:
MSDE is free version of SQL Server and used by AntiVirus software, backup softwares etc. Now, if there is no concept of instance, then you will land up in situation when you cannot install SQL Server if Antivirus is installed (or vice versa)
makes sense?
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