vRealize Orchestrator supports standalone mode and cluster mode. This design uses cluster mode.

vRealize Orchestrator supports the following server modes.

Standalone mode

vRealize Orchestrator server runs as a standalone instance. This is the default mode of operation.

Cluster mode

To increase availability of the vRealize Orchestrator services, and to create a more highly available SDDC, you can configure vRealize Orchestrator to work in cluster mode, and start multiple vRealize Orchestrator instances in a cluster with a shared database. In cluster mode, multiple vRealize Orchestrator instances with identical server and plug-in configurations work together as a cluster, and share a single database. 

All vRealize Orchestrator server instances communicate with each other by exchanging heartbeats at a certain time interval. Only active vRealize Orchestrator server instances respond to client requests and run workflows. If an active vRealize Orchestrator server instance fails to send heartbeats, it is considered to be non-responsive, and one of the inactive instances takes over to resume all workflows from the point at which they were interrupted. The heartbeat is implemented through the shared database, so there are no implications in the network design for a vRealize Orchestrator cluster. If you have more than one active vRealize Orchestrator node in a cluster, concurrency problems can occur if different users use the different vRealize Orchestrator nodes to modify the same resource.