Graphic Hub Terminal can operate in these modes:
Localhost is a single connection to a Graphic Hub (no dongle required). See Localhost, 5/4 Free, and Multiuser Configuration.
The 5/4 Free configuration provides five concurrent TCP/IP connections to a Graphic Hub (no dongle required, five TCP/IP connections excluding GH Terminal, GH Manager, GH Deploy Agent connections). See Localhost, 5/4 Free, and Multiuser Configuration.
The Multiuser configuration provides multiple concurrent connections to a Graphic Hub (dongle required). See Localhost, 5/4 Free, and Multiuser Configuration.
The Main Server, as with the Multiuser configuration, provides multiple concurrent connections to a Graphic Hub. The difference is that the Main Server provides a mirror service to a running a Replication Server. In a failover situation, the system automatically redirects all clients from the Main server to a Replication server (dongle required). See Cluster Configuration.
The Replication Server is use with the installation of a Main Server. A Replication Server is a duplication of the Main server. See Cluster Configuration.
Replications in a Graphic Hub mean that every transaction on the primary server is immediately mirrored on a Replication Server. In a failover situation, where the main server becomes unavailable, the system automatically redirects all clients from the Main Server to the Replication Server.
A failover situation occurs when one of the servers become unavailable due to hardware failure, software errors, power loss, etc. A Main server crash results in a failover situation, where the Main server switches to a Replication Server, in real-time.
On the Main server machine, the Graphic Hub Terminal shows Cluster Not Connected, and if the E-mail functionality is enabled, one or more error E-mails are sent.
Usually, a Graphic Hub in a Cluster configuration runs in real-time replication. In cases of a network overload, loss of another server in the Cluster, or other serious system instabilities, the Graphic Hub automatically switches to Recovery Mode. This means that one server buffers all necessary transactions, for example, saving files. The Graphic Hub then deploys these files to the other server in the Cluster when the resources are available again. After 15 seconds of no incoming transactions, the Graphic Hub switches to real-time replication again, and the data structure is updated, so that it is reflected on both servers.
If clients were directed to another server than the primary, during the down-time, the clients are re-directed to the primary server again.