# SQL Server - Upgrade

## **PaaS upgrade workflow** <a href="#sqlserverupgradeinplace-sqlserverpaasupgrade" id="sqlserverupgradeinplace-sqlserverpaasupgrade"></a>

### Request <a href="#sqlserverupgrade-request" id="sqlserverupgrade-request"></a>

The upgrade of a SQL Server PaaS instance is the responsibility of **cegedim.cloud**. Requests must be submitted via an [ITCare ticket](https://itcare.cegedim.cloud/support?createTicket=true\&step=Request\&requestTypeIndex=-1\&formName=DB_MSSQL), specifying a preferred time window for the operation.

Please indicate if the upgrade must be performed **outside of business hours**, to allow for proper RFC planning.

It is strongly recommended to first perform the upgrade in a **non-production environment**, to validate compatibility of the entire process with the client's technical and application constraints.

{% hint style="warning" %}
Upgrades of SQL Server clusters **older than version 2016** are **not supported** by **cegedim.cloud**.

This limitation is due to major changes introduced in the SQL Server engine starting with version 2016, particularly regarding AlwaysOn features and the deprecation of legacy components.

> Major version upgrades (e.g., from SQL Server 2019 to 2022) require a different approach, namely the full reprovisioning of the environment. In this case, a **new PaaS instance** must be provisioned with the target version, followed by a **manual migration of databases**.

> This process only covers the application of **Cumulative Updates (CU)** published by Microsoft. These updates contain security, stability, and performance fixes for SQL Server.
> {% endhint %}

### Process <a href="#sqlserverupgrade-procedure" id="sqlserverupgrade-procedure"></a>

The upgrade process involving Cumulative Updates follows these steps:

1. **Snapshot of virtual machines** (to enable rollback in case of failure)
2. **Full backup** of customer databases using Rubrik
3. **Installation of SQL Server Cumulative Updates** (official Microsoft patches)
4. **Server reboot** to apply the updates
5. **Integrity checks** on databases and review of error logs

For **AlwaysOn clusters**:

* Secondary nodes are patched first
* A **manual failover** to the secondary node is performed prior to updating the primary
* **Controlled reboot** of the updated node
* The process is repeated for remaining nodes

### Impacts <a href="#sqlserverupgrade-impatcs" id="sqlserverupgrade-impatcs"></a>

Applying Cumulative Updates can lead to temporary service interruptions or changes in application behavior.

Points to consider:

* **Temporary unavailability** of SQL Server during reboot
* Risk of **functional regressions** due to internal behavior changes in CU
* Possible rollback required if installation fails

**Potential risks:**

* Failure to rejoin the AlwaysOn cluster
* Data corruption if backups are invalid
* Broken application dependencies due to changes introduced by the CU

### Estimated Duration <a href="#sqlserverupgrade-estimatedduration" id="sqlserverupgrade-estimatedduration"></a>

The duration of an upgrade depends on several factors, including the **data volume to be backed up** and the **deployment mode** (standalone vs AlwaysOn).

Estimated durations:

* Standalone instance with low volume: **\~1 hour**
* AlwaysOn cluster with failover: **\~2 to 3 hours**

> These durations are indicative only and should be adjusted according to the specific constraints of the target environment (I/O, load, network latency, etc.).

## Operating System Updates <a href="#sqlserverupgrade-operatingsystemupdates" id="sqlserverupgrade-operatingsystemupdates"></a>

Windows Server updates are performed exclusively during scheduled **"Patch Parties"**—maintenance windows during which critical security and stability patches are applied in a coordinated manner, in line with **cegedim.cloud**'s maintenance schedule.

These operations are **outside the scope** of the SQL Server upgrade. If an OS version change is required, the following steps must be taken:

* Request **reprovisioning** of a PaaS instance with the new OS version via ITCare
* Perform a **manual migration** of the databases to the new instance

> In-place upgrades of the operating system are **not supported**.


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