What Happens when a Failover Occurs?

When a failure is detected, the active node goes into a standby state, and the standby node goes into an active state. A list of what happens during each change of state is described below.

When the active node goes into a standby state:

• SAC goes into a standby state, blocks stop being processed.
• If enabled, Alarm ODBC pauses from processing messages.
• The SCADA Synchronization process (SCADASync.exe) stops pushing data to the standby SCADA node.
• The active node switches its role (via SCADARoleMgr.exe) to become the standby SCADA node.

When the standby node goes into an active state:

• SAC goes into an active state, block processing begins.
• The standby node switches its role (via SCADARoleMgr.exe) to become the active SCADA node.
• Alarm ODBC begins processing messages.
• The SCADA Synchronization process (SCADASync.exe) begins to synchronize with the standby SCADA.