Applying the latest patches to SQL Server, Windows OS, and underlying hardware is a vital part of maintaining secure, high-performing systems. For many organizations, this is done on a regular schedule—monthly, quarterly, or aligned with specific maintenance windows. However, for business-critical, 24/7 systems, patching takes extra planning and vigilance.

Here’s a straightforward look at patching strategies and considerations:

Regular Maintenance Is Key

For High Availability (HA) setups or environments using Always On Availability Groups (AAG), scheduling monthly failovers for maintenance is ideal. This ensures:
# SQL Server, Windows OS, and firmware/hardware stay up-to-date.
# Downtime is minimized, and systems remain resilient against known vulnerabilities.

Skipping updates for long periods can lead to performance degradation, security risks, and compatibility issues. I love to be proactive in this space, it’s my duty as a DBA!

CU vs. GDR: What’s the Difference?

When patching SQL Server, there are two main types of updates to consider:

Cumulative Updates (CU):
Include all fixes, such as performance improvements, feature updates, bug fixes, and security patches. CUs are ideal for staying current and ensuring systems are optimized.

General Distribution Releases (GDR):
Provide security-only updates, focusing on critical vulnerabilities. GDRs are the safer, more conservative choice, particularly for environments that prioritize stability over new features.

Choosing the Right Updates:
# Stick with GDR if your environment has only applied GDR updates in the past and prioritizes minimal change.
# Use CUs for broader improvements and enhancements, but test thoroughly before deploying.

Patch Tuesday and Update Frequency

Microsoft’s Patch Tuesday is a key date to monitor.

Newer SQL Server versions: Updates arrive every 1–2 months, typically including CUs.

Older SQL Server versions: Updates are less frequent, often limited to GDR releases for security.

The challenge is staying current: while being on the latest CU or GDR means benefiting from fixes, it also carries risks if an update introduces new bugs.

What Happens When a Patch Goes Wrong?

No update is perfect—Microsoft occasionally releases patches that cause unexpected issues. If a patch creates problems:

1. Roll back the update to restore stability.
2. Test thoroughly in a non-production environment before redeploying or applying future updates.

Best Practices for 24/7 Systems

For business-critical systems:

1. Keeping up to date means more than just SQL Server. It includes Windows OS, firmware, and hardware drivers, which should/will be included in the maintenance plans.

2. Prioritize regular maintenance cycles with clear testing and rollback procedures. Roll-out to non-Prod environments before applying to Production.

3. To achieve no downtime for SQL Server patching, we use HA/AAG configurations to minimize disruption during failovers or patching.

Hope all this was useful info!