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Hot-Standby |
Hot-Standby is a feature that allows implementing a fail-over concept in a supervisory system. This concept consists in a possibility of having two servers, main and backup, one acting as a contingency of the other, that is, if a main server fails, a backup server immediately starts executing, with no losses in this process. This is known as a server in Standby mode.
Thus, Elipse E3 Hot-Standby tool aims at allowing a server to remain in a standby status, waiting for a possible failure of another server, an active server. Switching to an active server can be manual or automatic.
A manual switching is activated via E3 Admin menu on Windows Notification Area of the standby computer, in the Server - Activate option. An automatic switching occurs when a server in Standby mode detects that a main server is not executing anymore. A server can assume one of the following statuses:
•Server under Maintenance: This status is indicated in Domain server's settings. A server under maintenance does not participate in any Domain event
•Active Server: Only one server can be active in a Domain at a certain time. An active server is the one executing the application (E3 Admin)
•Standby Server: Only one server can be in Standby mode in a Domain at a certain time. A server in Standby mode executes E3 Admin in Standby mode, and an application remains loaded, only waiting for a command to start operating. A backup server monitors an active server, and if it is not answering, the server in Standby mode is then activated
•Inactive Server: A server switches to inactive when it is declared in a Domain, but it is neither selected as the main nor as the backup server. Even when inactive, this server monitors changes in a Domain file, and it may switch to an Active or Standby status if the Domain is reconfigured
IMPORTANT |
To execute a redundant application in Elipse E3, all servers must execute the same product version, and also must have a local updated copy of Domain files, that is, .prj and .lib files, among others. A .dom file, however, is automatically synced by E3 Server, that is, changes made to a .dom file on one server are automatically copied to this .dom file on other Domain servers. To do so, a .dom file must exist at the same path on all servers. |
Hot-Standby uses a REC connection, therefore it only works if E3 Server is started up on all computers involved in this communication.
If an Elipse E3 Studio user or a Hot-Standby user is also an administrator of a remote computer executing E3 Server, they can remotely control this service by using services.msc, via the Action - Connect to another computer option.