A tier is a unit in the Splunk AppDynamics model composed of a grouping of one or more nodes. How you organize tiers depends on the conceptual model of your environment.

Often a tier is used to a group of a set of identical, redundant servers. But that is not strictly required. You can group any set of nodes, identical or not, for which you want performance metrics to be treated as a unit into a single tier.

The single restriction is that all nodes in a single tier must be the same type. That is, a tier cannot have mixed types of agents, such as both .NET and Java nodes.

The traffic in a business application flows between tiers, as indicated by lines on the flow map, which are annotated with performance metrics.

In the Splunk AppDynamics model:

• There is no interaction among nodes within a single tier
• An application agent node cannot belong to more than one tier