In Enhanced Failover, Maintenance Mode allows you to temporarily suspend synchronization between the two SCADA nodes in order to make on-the-fly configuration changes to the process database. After entering Maintenance Mode, you can make modifications to the database on the primary SCADA node. During this time, the secondary SCADA node is fully runtime functional and carries all the iClients. Operator interaction from the iClients, such as alarm acknowledgments and outputs, are performed through the secondary SCADA node and recorded in the secondary SCADA database. When Maintenance Mode is exited, operator interactions on the database in the secondary SCADA node are synchronized to the primary SCADA node before the primary SCADA node becomes active and starts to synchronize the database to the secondary SCADA node.
By default, Maintenance Mode synchronization and corresponding time-out parameters are enabled. To disable Maintenance Mode Synchronization, refer to the Disabling Maintenance Mode Synchronization section.
Alarm Acknowledgement Synchronization
Alarm acknowledgement synchronization uses the iFIX local area network connection, which must be a stable working connection between the SCADA nodes for the alarm acknowledgment synchronization to complete successfully.
A successful alarm acknowledgment synchronization returns the following message on the Overview page of ScadaSyncMonitor on the primary node:
Updated Alarm Acknowledgements
An unsuccessful alarm acknowledgment synchronization may return the following message on the Overview page of ScadaSyncMonitor on the primary SCADA node:
Updated Alarm Acknowledgments with Read Errors
Updated Alarm Acknowledgments with Write Errors
Read errors occur when the primary SCADA node cannot read alarm acknowledgements from the secondary SCADA node. Check iFIX networking to ensure that the primary and secondary SCADA are connected. Write errors occur when the primary SCADA node cannot write alarm acknowledgements, perhaps because the tag it tried to write to does not exist.
Simulation Register Synchronization
Simulation registers are synchronized over the dedicated network for SCADA synchronization. This includes the SIM driver registers, SIM signal generators and parameters, and SM2 driver registers.
A successful simulation register synchronization returns the following message on the Overview page of ScadaSyncMonitor on the primary node:
Updated Simulation Registers
If the primary SCADA node does not receive simulation register synchronization from the secondary SCADA node within the timeout period (the default is 10 seconds), it exits Maintenance Mode without synchronizing. An unsuccessful simulation register synchronization indicates that the SCADASync connection may be broken and returns the following message on the Overview page of ScadaSyncMonitor on the primary SCADA node:
Maintenance Mode Synchronization Timed Out, Check Scada Sync Communication.
