> 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/database-engines/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 service status.

***

## How do I know when a patch is available?

**Patch Available** appears next to the service status on the My Services dashboard and the database service home page. Hover over it and click **Patch Now** to view the available versions.

***

## How do I apply a SQL Server patch?

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

1. Hover over **Patch Available** next to the service status → click **Patch Now**.
2. In the **Patch Database Engine Version** window:
   1. Choose the target SQL Server version from the dropdown list.
   2. (Optional) Adjust the number of instances to patch if the service has more than one instance. By default, all instances are included. The primary and HA instance are always updated together — you cannot deselect the HA instance from the primary.
   3. Review the estimated service downtime shown in the dialog.
   4. Select the **Patch Database Engine Version** checkbox.
   5. Click **Start Patch**.

Tessell then performs the following steps automatically:

1. Submits the request to patch DB service instances from the older to the new version.
2. Installs the new version of SQL Server binaries.
3. Patches the DB service instance(s).
4. Sets the service status to **Ready** and updates Tessell metadata.

***

## How does Tessell minimize downtime during HA patching?

For HA services, Tessell uses **Standby-First patching with rollover mode**, minimizing downtime to only the switchover window.

By default, there is one switchover during the patching operation, and the roles of the instances are swapped at the end of patching (the patched standby becomes the permanent primary).

> **Note:** If you want the original primary and standby roles restored after patching, contact Tessell support to enable the role-restore feature flag. When enabled, a second switchover is triggered at the end of patching to restore the original roles.


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