> For the complete documentation index, see [llms.txt](https://docs.tessell.com/tessell/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tessell.com/tessell/tessell-for-sqlserver/db-services/my-services/patching-sqlserver.md).

# Patching

If a higher patch version is available from Tessell, **Patch Available** appears next to the status. To view the new versions available for your DB Service, hover over **Patch Available** and then click **Patch Now**.

> **Note**: Tessell highly recommends taking a snapshot of the database before patching to prevent any data loss.

A **Patch Database Engine Version** window pops up where you can:

1. Choose a version of the database engine available from the dropdown list.
2. Optionally, edit the number of instances to patch if the service has more than one instance. By default, all the instances are patched. The primary and HA instance update together, you cannot deselect HA instance from the primary.

   An estimated service downtime is displayed for patching.
3. Select the **Patch Database Engine Version** check box.
4. Click **Start Patch**.

The request to apply the patch is updated and the following steps take place automatically:

* Request is submitted to patch the software for DB service instances from older version to new version.
* Installs the new version of SQL Server binaries.
* Patches the DB Service Instance(s).
* Service is ready and updates the Tessell metadata.
* For HA Services, Tessell follows Standby-First patching with rollover mode, minimizing the downtime only for the "Switchover". By default, there is one switchover during patching operation and the roles of instances are changed at the end of patching. If the customer intends to have the primary and standby instances as-is role post patching, please ask Tessell support to enable this feature flag. If this feature flag is turned on, another switchover is triggered at the end of patching.


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