What is a Zone? (In the context of XenApp)

In the XenApp 5 architecture there are 6 essential components
1. Xen App Servers
2. Data collector
3. Zones
4. Data Store Database
5. License Server
6. Web Interface Server

Zones

A logical group of XenApp servers communicating with a single data collector is called a zone. Zones are typically based on subnets.

During the installation of XenApp on a server, the server must join a zone. The first XenApp server installed in a server farm defines the initial zone and becomes the data collector for the zone. The default name of the first zone is Default Zone. After the installation is complete, an administrator can create additional zones and move servers into the different zones. The first XenApp server moved into a zone becomes the data collector for that zone.

Zones can enhance the performance of a server farm by allowing related servers to be grouped, regardless of their network subnet. Zones can be used to:

Designate physical or logical groupings.
Enable zone preference and failover.

source: XenApp5 courseware