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techresearch7777777-7743 avatar image
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techresearch7777777-7743 asked Criszhan-msft edited

Uninstall 2nd unused SQL Server instance ?

Hello, noticed we have an active server that two SQL Server instances (default MSSQLSERVER & SQLDEV) installed.

Default MSSQLSERVER is being used and the other SQLDEV is not...is in the Stop state.

We would like to uninstalled the unused SQLDEV instance and was wondering if it's possible, steps to take, and concerns to be aware of any impacts that might affect the other current active instance default MSSQLSERVER.

Thanks in advance.

sql-server-general
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cooldadtx avatar image
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cooldadtx answered

Yes you can uninstall the unused instance and it is a good idea to do so. When you install SQL it installs a set of shared components and the SQL instance specific components. When you run the installer again choose the Remove option and it'll ask if you want to remove shared components or a specific instance. Select the instance you want to remove and then it'll give you the option to remove the particular features of the instance (DB, SSRS, etc). If you want to completely remove the instance then ensure all the features are selected for the instance (IIRC there is a button for that). It'll then remove the instance and related services but any remaining instances and the shared components will remain.

Note that it will not delete data files and whatnot so after the uninstall is complete you will still likely have some folders with the instance name in them. If you don't need them then you can remove them manually.

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techresearch7777777-7743 avatar image
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techresearch7777777-7743 answered cooldadtx commented

Thanks cooldadtx for your reply.

Currently the 2nd instance is in the Stopped state so is it ok to uninstall in this state?

Also will it affect the main 1st MSSQLSERVER default live instance...i.e. downtime/inaccessible, slow performance, Blocking, etc... ?

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Yes you can uninstall the second instance.

No it won't have any impact on the first instance. Of course during the uninstall, like running any other application, there will be a slight increase in CPU, memory usage and IO access but it shouldn't really impact the existing instance unless your server is already running out of resources.

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Criszhan-msft avatar image
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Criszhan-msft answered Criszhan-msft edited

Hi @techresearch7777777-7743,


When uninstalling this unused SQL Server instance you only need to select the instance features such as the database engine services and replication, and do not select other shared features, It will not affect other instances. The Memory, CPU, and Disk utilization will increase temporarily when the instance is uninstalled(or install), but the impact is small.

It is best practice to stop the SQL Server services before uninstalling the SQL Server instance.

I tested uninstalling some SQL Server instances(2017 and 2019)with the SQL Server installation wizard(Setup), the default folder selected during the installation of these instances will still be saved ( For example, C:\Program Files\Microsoft SQL Server\MSSQL15.SQLEXPRESS), but the data files of the system database will be cleared and the user (or distribution) databases will not.
So if necessary, please back up the system databases on the instance.
https://docs.microsoft.com/en-us/sql/sql-server/install/uninstall-an-existing-instance-of-sql-server-setup?view=sql-server-ver15&tabs=Windows10

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