Primary vs additional Regions - Amazon Directory Service
Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

Primary vs additional Regions

With multi-Region replication, Amazon Managed Microsoft AD uses the following two types of Regions to differentiate how global or Regional features should be applied across your directory.

Primary Region

The initial Region where you first created your directory is referred to as the primary Region. You can perform only global directory level operations such as creating Active Directory trusts and updating the AD schema from the primary Region.

The primary Region can always be identified as the first Region showing at the top of the list in the Multi-Region replication section, and ends with - Primary. For example, US East (N. Virginia) - Primary.

Any changes that you make to Global features while the primary Region is selected will be applied across all Regions.

You can only add Regions while the primary Region is selected. For more information, see Add a replicated Region.

Additional Region

Any Regions that you have added to your directory are referred to as additional Regions.

Although some features can be managed globally for all Regions, others are managed individually per Region. To manage a feature for an additional Region (non-primary Region), you must first select the additional Region from the list in the Multi-Region replication section on the Directory details page. Then you can proceed to manage the feature.

Any changes that you make to Regional features while an additional Region is selected will be applied only to that Region.