vRealize Orchestrator supports standalone mode and cluster mode. In this design, vRealize Orchestrator is automatically in standalone mode because the environment contains one vRealize Automation appliance running an embedded vRealize Orchestrator.

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. When you join the vRealize Automation appliances in a cluster, the vRealize Orchestrator instances embedded in them are automatically clustered.

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 as non-responsive, and one of the inactive instances takes over to resume all workflows from the point at which they are 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.