Steps for sql server decommission activities.

How to decommission sql Instances from the server?

Before uninstall we need to follow some steps.

1. Make a note of service pack and hot fixes installed.

2. Backup the databases master, msdb, and model to be used for roll back purpose.

How to check which Service Pack installed?

Run below SQL Server command

SELECT SERVERPROPERTY('productversion')

, SERVERPROPERTY ('productlevel')

, SERVERPROPERTY ('edition')

GO

If you’re using SQL Server version 7, you need a different command:

SELECT @@VERSION

GO

How to find which Hotfix applied on SQL Server?

To determine the Hotfix number, since each one will be different, and many may be installed. To determine the Hotfixes on your server, download the program called HFNetChk (http://support.microsoft.com/kb/305385) from Microsoft. There’s a commercial version of this tool by the way that will keep your servers up to date, but this is the free one Microsoft provides.

There are now stored procedures you can use to show you the build number on your server, such as:

EXEC sp_server_info 

GO

and 

EXEC master..xp_msver

GO

Steps to be followed for uninstall sql server:

1. Uninstall SQL Server through Windows Control PanelàAdd/remove Programs.

    a. Uninstall SQL Server patches in descending order

    b. Uninstall SQL Server installation

2. Restart server

Steps to be followed for re-intstall the old sql server.i.e(roll back)

1) Reinstall SQL Server.

2) Apply any service packs and hotfixes that were installed earlier.

3) Restore the databases master, msdb, and model from the last backup that was taken before you installed.

When we go for decommission of Sql instances?

If current application has been migrated to sql farm servers or other environment, then existing systems will not being used. So we need to uninstall sql server instances from the server.