Active Manager
Active Manager runs as part of the Microsoft Exchange Replication service (MSExchangeRepl, not to be confused with MRS, the Mailbox Replication service) on every Mailbox server. Both the Replication service and Active Manager are present on Mailbox servers that don’t belong to a DAG, in which they are essentially in a standby role waiting for the server to join a DAG (which it might never do). Conceptually, Active Manager is the orchestrator for native-mode high availability in Exchange because it decides which database copies are active and which are passive, taking into account administrator preferences such as the database activation preference order. You can regard Active Manager as the successor of the resource management model ...
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