Understand hot backups

The hot backup provides a single name (hot backup pair name) that points to two alarm providers, the primary and the backup (the hot backup pair). The InTouch HMI alarm consumers can reference this single hot backup pair name and retrieve alarms from either the primary or the backup alarm provider. The following alarm clients support querying the hot backup pair:

• InTouch HMI Alarm DB Logger Manager

• InTouch HMI Alarm Printer

• InTouch HMI Alarm Viewer Control

• Alarm Client Control

If both provider nodes are operating normally, the alarm consumer receives alarm data from the primary provider. If the primary provider fails, however, the alarm consumer receives alarm data from the backup instead. You can also configure the Hot Backup Manager to continue using the backup provider even when the primary provider is available. If this backup option is not selected then, when the primary provider is available the Backup manager will switch to the primary provider automatically. For more information, see Create a hot backup pair.

The following figure shows how the alarm consumer still receives alarms after the primary alarm provider fails. The alarm consumer still references the hot back pair, but the backup provider provides the alarm data.