Related terms
An agent is an internal background process operating on the server that runs activities on a periodic basis. Agents route work according to the rules in your application; they also perform system tasks such as sending email notifications about assignments and outgoing correspondence, generating updated indexes for the full-text search feature, synchronizing caches across nodes in a multiple node system, and so on.
Agents are autonomous and asynchronous: the activities they call run individually on their own schedules, and a second activity execution can start before one started earlier completes.
Agents are defined by Agents rules (Rule-Agent-Queue rule type). Agents are enabled and scheduled through Agent Queue data instances (Data-Agent-Queue class). In a multinode cluster, an agent can run on multiple nodes — even each node, to achieve high throughput, if potential deadlock and similar locking issues are correctly handled by the activities.
A legacy agent — one for which the Queue Mode setting on the Schedule tab is Legacy — is an agent that does not use queues, but processes each item to completion in a single pass. Agents created in releases before V5.4 first appear as legacy agents in later releases, until they are upgraded to Standard.
Your system contains nine (or more) agents rules when initially installed. This help system contains a topic for each.