What is a DAG (Database Availability Group) in Exchange Server?

A Database Availability Group (DAG) in Exchange Server is a critical feature designed to provide high availability for database copies. It allows for automatic failover of mailbox databases in the event of a failure, ensuring that users can continue to access their emails with minimal disruption.

DAGs consist of multiple mailbox servers that host mailbox databases, and they can maintain multiple copies of these databases across different servers. This setup ensures that if one server goes offline due to hardware failure or maintenance, another server within the group can take over seamlessly, providing continuous access to the mailbox data.

The architecture of DAGs enhances overall resilience and protects against data loss. Each server in the group monitors the health of the database copies, and if it detects a problem, it can automatically switch to a healthy copy, thereby maintaining service availability.

In contrast, the other options describe functionalities not related to DAGs. For instance, while encryption can be relevant in securing email communications, it does not relate to the high availability features offered by DAG. Similarly, a user interface type or a backup protocol for mailboxes focuses on different aspects of email management and data protection that do not pertain to the core purpose of a DAG.