Understanding SQL Server Patching: GDR versus CU

Introduction:

Are you curious about the distinctions between GDR and CU when Microsoft releases a KB article with new fixes or security updates? In this article, we'll delve into the details and provide some helpful tips along the way.

Setting the Stage: GDR versus CU:

Let's begin by understanding Microsoft's explanation:

Microsoft defines the General Distribution Release (GDR) and Cumulative Update (CU) designations as two different servicing options for SQL Server baseline releases, which can be either an RTM release or a Service Pack release.

Determining the Baseline:

To determine your SQL Server's baseline version, you can use various methods. One way is by executing the following T-SQL code:

SELECT @@VERSION;

Alternatively, you can check the version by examining the sqlserver.exe file in the corresponding \Binn directory of your installation. Another option is using the SERVERPROPERTY() function for more detailed version information, but that is beyond the scope of this post. Additional resources at the end of this article provide further information on this topic.

Understanding SQL Server Version Numbers:

The version numbers in SQL Server are referred to as "build numbers" and can be found in the following table:

SQL Server version Build number

SQL Server 2000 8.0.*

SQL Server 2005 9.0.*

SQL Server 2008 10.0.*

SQL Server 2008 R2 10.50.*

SQL Server 2012 11.0.*

SQL Server 2014 12.0.*

SQL Server 2016 13.0.*

SQL Server 2017 14.0.*

SQL Server 2019 15.0.*

SQL Server 2022 16.0.*

GDR Updates: Focused on Security:

GDR updates are cumulative and exclusively include security updates for the given baseline. They do not introduce new features or fixes apart from what is deemed necessary for security purposes.

CU Updates: A Mix of Fixes and Security Updates:

On the other hand, CU updates are also cumulative but encompass both functional fixes and security updates for the given baseline.

Noting the "Baseline" Concept:

It's crucial to emphasize the concept of a "baseline," which can be an RTM release or a Service Pack release. Starting from SQL Server 2017, Service Pack releases are no longer available, leaving only RTM and CUs as options. Thus, one can begin with the RTM version and apply either GDRs exclusively or both GDRs and CUs. For those using older versions before SQL Server 2017, Service Packs should be considered as baselines as well.

Cautionary Note:

When starting fresh from a baseline, you can choose to apply either GDR or CU based on your policy or planning. If your intention is to deploy only GDRs, it is essential to avoid applying any CUs. However, it's important to note that this transition from GDR to CU can only occur once, after which you will be on the CU side of things.