The replication agents carry out many of the tasks associated with replication including creating copies of schema and data, detecting updates at the Publisher or Subscriber, and propagating changes between servers. Each replication agent has an agent profile associated with it, agent properties that you can set, an agent schedule, and an agent history.
Replication Monitor provides the capability to administer replication agent activity graphically. You can view a list of all the Snapshot, Log Reader, Distribution, Queue Reader, or Merge Agents supported by a Distributor. You can select a Distributor and click Replication Monitor to display a list of agents. When you click the folder for a specific type of agent, all the agents of that type on the Distributor are displayed. You can then view the detailed activity of a specific agent.
Independent and Shared Agents
An independent agent is an agent that services one subscription. Latency is reduced when using independent agents because it is ready whenever the subscription needs to synchronize.
A shared agent services multiple subscriptions, and is the default for snapshot replication or transactional replication. When multiple subscriptions using the same shared agent need to synchronize, they wait in a queue, and the shared agent services them one at a time.
All of the agents used during merge replication are independent agents. When using independent agents with snapshot replication or transactional replication, you must take care to prevent transactions that have interdependencies from being delivered out of sequence.