What are the basic building blocks of GTM?

Short answer

GTM consists of three nested objects and the device-wide definitions they use. The queries are received by the DNS Service; the service hosts one or more domains, and under each domain are the records that produce the answer. Which address the records return is decided by Health Checks, Health Scenarios and Remote Devices (Data Centers); Trigger Actions, Express Profiles (DNS Integration) and DNS Forwarder Profiles establish the connection with external systems. These definitions are made once and used in all DNS services.

How Does It Work?

Building block	What it does	Where it is bound
DNS Service	The authoritative listener that receives the queries on the Frontend IP and Port	The domains are bound to it
Domain	The zone for which the service is authoritative; carries the operating mode (Default Mode) and the data center groups	A DNS Service
Record	The answer unit that carries the addresses, the HC condition per address, the Balance Algorithm and the Fail-Safe Records	A domain
Health Checks	Measures the status of an address or of a data center	Health Scenarios
Health Scenarios	Combines health checks into a single decision with AND / OR	The HC condition of the addresses in the record, the Disaster Recovery switchover condition
Remote Devices (Data Centers)	Defines the TR7 devices in the other data centers and collects their access statuses and metrics; produces automatic health checks for each of them	The data center groups of the domain
Trigger Actions	Calls an external HTTP, HTTPS or Oracle target when a scenario becomes active or passive	Health Scenarios
Express Profiles	Pulls the records from an existing DNS server with zone transfer	The data center group of the domain
DNS Forwarder Profiles	Forwards the queries for which the service is not authoritative to upstream DNS servers	DNS Service

Industry equivalents: domain corresponds to the zone or wide IP concept, record to resource record or pool, Health Checks to monitor, and Remote Devices to data center or site (object model).

In TR7

• All of them are in the Configuration Menu → GTM tab: in the GTM Services card, Service Management and the service names; then Remote Devices (Data Centers), Health Checks, Trigger Actions, Health Scenarios, Express Profiles (DNS Integration) and DNS Forwarder Profiles.
• Domains and records are managed not in a separate menu but in the Domains and Records tabs on the service's own screen.

Common Misconceptions

• "Health checks are bound directly to the record." In the HC condition of the address in the record, Static, Disabled or a health scenario is selected; health checks are bound to the record through the scenario (What is a health scenario; how does it combine several checks?).
• "Each DNS Service defines its own health checks." Health Checks, Health Scenarios and the profiles are device-wide; all services use the same definitions.
• "The mode is selected per record." The mode is selected on the domain and applied to all records of the domain (What is the difference between the Standalone, Disaster Recovery and Datacenter modes?).

How it is done in the documentation

• GTM (Global Traffic Manager) · Core Building Blocks
• GTM (Global Traffic Manager) · Object Model
• GTM (Global Traffic Manager) · Terminology

Related questions

• What is a DNS Service in GTM?
• What is a domain in GTM; how does it relate to a DNS Service?
• What is a DNS record in GTM; which record types are supported?
• What is a Remote Device; how does GTM monitor a remote data center?