Exchange Server Active Manager (SAM) is a new component in Microsoft Exchange Server 2010 and later versions. SAM manages database transactions and failover processes within a DAG (Database Availability Group). SAM essentially “traffic police“ It acts as a database manager. All database mounts, dismounts, moves, and failover requests go to SAM, and SAM responds to these requests. This makes database state changes more predictable and manageable.
SAM operates with two main components: Active Manager Client and Active Manager Server. Active Manager Client communicates with Active Manager Server via RPC. Active Manager Server runs on each Exchange Server and handles RPC requests.
SAM has two modes: Standalone and DAG.
- In standalone mode, SAM only manages the database mount and dismount for that machine.
- In DAG mode, SAM additionally manages the failover processes. Within the DAG, one SAM instance takes the role of PAM (Primary Active Manager) while the others take the role of SAM (Standby Active Manager).
Primary Active Manager (PAM):
PAM manages database assemblies and failover operations for a DAG. PAM is typically on the node that owns the DAG's quorum resource model. In the event of a failover, the PAM role is automatically moved to the new quorum resource model owner.
Standby Active Manager (SAM):
SAM is the Active Manager role that runs on each DAG node. SAM manages local database mounts and failover operations. It also monitors a node's ability to be a PAM, and if PAM fails, SAM automatically takes over the PAM role.
SAM and Failover:
When a DAG node experiences a failure, SAM automatically initiates the failover process. SAM monitors the status of all database copies in the DAG and evaluates a set of criteria to determine the best copy. In the event of a failover, SAM automatically selects and mounts the best copy.
Specifically, in the event of a failover, SAM examines all available database copies and selects the copy that contains the latest data and the fewest errors. This ensures that the failover process is fast and reliable, and minimizes data loss.
Now that we have defined the Active Manager, we can focus on the Database Availability Group (DAG) scenario.
Let's say you have an Exchange Server cluster and you have a 2 node DAG setup in this environment. The nodes are named "EXCH01" and "EXCH02". You also have 2 mailbox databases, "DB1" and "DB2".
Both databases are actively running on node “EXCH01” and have passive copies on node “EXCH02”. In this case, node “EXCH01” takes the role of Primary Active Manager (PAM) while node “EXCH02” takes the role of Standby Active Manager (SAM).
Suddenly, a problem occurred on node “EXCH01” and the server went offline. In this case, Active Manager comes into play and SAM on node “EXCH02” detects that node “EXCH01” is offline and automatically takes over the PAM role.
Next, follow Active Manager, makes passive copies of databases “DB1” and “DB2” active on node “EXCH02”. This process is a failover process and occurs under the management of Active Manager.
This ensures that users have uninterrupted access to their emails because Active Manager ensures continuity of Exchange services even in the event of a server crash. This scenario shows how critical a role Active Manager plays in Exchange Server.
Conclusion
Active Manager, Exchange ServeIt is a critical component to ensure r's high availability and durability features. Active Manager's powerful failover capabilities, a Exchange Server It ensures that the environment operates continuously, and even failures on a single node do not interrupt this continuity.