Differences Between Enhanced Failover and Failover in Previous iFIX Releases

The Enhanced Failover configuration and architecture provided in iFIX 5.0 and greater is different compared to previous iFIX versions. If you are a new customer or a customer upgrading from a previous version of iFIX, be sure to allot some time to understand these changes and implement the new configuration.

Some of the Enhanced Failover features provided in iFIX 5.0 and greater include:

Changes in iFIX 2023

Some of the changes introduced in iFIX 2023 for Enhanced Failover include:

  • If the Primary SCADA fails over to the Secondary due to a shutdown or connection loss, the Secondary will remain active when the Primary comes back online. To make the Primary the active SCADA again, you must execute a manual failover using one of the SWITCHSCADAROLE fields of the Network Status Display (NSD) tag.

Updated Licensing

Enhanced Failover is a keyed option in iFIX 5.0 and greater. New and upgrade customers must ensure this option is enabled on your key before starting iFIX. You can check if this option is enabled through the License Viewer.

Enhanced Failover and Legacy Client Compatibility

An iFIX network that contains iFIX version 5.8 Enhanced Failover SCADA nodes and also contains older iFIX client nodes may not be supported:

  • An iFIX client node, installed with iFIX version 5.5 or later, is fully compatible with iFIX version 5.8 Enhanced Failover SCADA nodes.
  • An iFIX client node, installed with iFIX version 5.1 and updated with iFIX51_Pulse10_Workspace_019 SIM (Software Improvement Module), is fully compatible with iFIX version 5.8 Enhanced Failover SCADA nodes.  
  • An iFIX client node, installed with iFIX version 5.1 and is not updated with iFIX51_Pulse10_Workspace_019 SIM is not compatible with iFIX version 5.8 Enhanced Failover SCADA nodes.
  • An iFIX client node, installed with iFIX version 5.0 or earlier, is not compatible with iFIX version 5.8 Enhanced Failover SCADA nodes.  

IMPORTANT: In an Enhanced Failover pair, both SCADA nodes must have the same iFIX version installed with all SIMs.  

More Robust and Efficient Processing

Enhanced Failover is more robust than in earlier versions before iFIX 5.0. For instance, in previous releases, the two SCADA systems acted independently of one another. Now, the active and standby nodes stay synchronized and the detection of failure occurs more quickly.

Before iFIX 5.0, generated alarms could vary based on differences in timing of the two independent nodes. This process was improved, so that such inaccuracies are minimized.  

Support for Database Synchronization

Enhanced Failover includes database synchronization between the active and standby SCADA pair.

If you are upgrading from a previous iFIX release, prior to iFIX 5.0, make sure you read the Enhanced Failover and Upgrading section of the iFIX Getting Started guide, for a complete list of items that you should evaluate.

True Standby Node Support

In the iFIX releases prior to 5.0, each node in a pair was active all the time. It was left to the customer to create a scheme that simulated an active and a standby node. With Enhanced Failover, the secondary node is a dedicated standby node. As such, the standby node is in an inactive state:

  • The SAC database processing task is in standby mode, and no longer processing the database.
  • Outputs are not being written to the PLC.
  • Interactive or programmatic process database changes are not allowed, as they would be overwritten by the synchronization process.
  • The Alarm ODBC client is not writing messages to the relational database.

This means that you can no longer use your standby node (which used to be called a backup node) as your development node, if you did so in the past.

Dedicated SCADA-to-SCADA Network for Improved Communications

Between the active and standby nodes, iFIX now supports (and GE strongly recommends) a dedicated connection between them – a dedicated SCADA-to-SCADA network. This requires that you install new hardware, if you are upgrading from a previous release, as well as that you update your SCU configuration. The use of a dedicated network creates a fast, reliable, efficient connection between the two SCADA nodes for use with synchronization traffic. A dedicated network allows you to eliminate synchronization traffic from your iClient network, eliminate a single point of failure, and improve performance.

Automatic Switching to Active SCADA

All iClient nodes automatically switch to the active SCADA. Connection failover can be manually initiated using the CURACTIVENODE field of the NSD tag, but an iClient is automatically switched back to the active SCADA node.

New NSD Tag Fields

New fields for Network Status Display (NSD) tag are available for use in iFIX pictures and applications. You can only access this tag when TCP/IP networking is enabled. The new Network Status Display (NSD) fields include:

  • A_SCADASTATUS, F_SCADASTATUS – The status of the SCADA node: ACTIVE (1) or STANDBY (2).
  • A_SWITCHSCADAROLE, F_SWITCHSCADAROLE – Use this to request a change in state: ACTIVE (1) or STANDBY (2).
  • F_SCADAREDUN – This field is set to 1 if Enhanced Failover is enabled; it is set to 0 if it is disabled.  

For more information on the NSD fields, refer to the Network Status Display Fields section.

Alarm Acknowledgement Synchronization Change

In the iFIX releases prior to 5.0, the failover feature attempted to keep alarms synchronized using the ALM_SYNC process. Now, with Enhanced Failover, this feature is part of the database synchronization process. ALM_SYNC is therefore obsolete and no longer required to keep alarms synchronized.

New Enhanced Failover Runtime Information Fields

The runtime information fields for Enhanced Failover reside within SCADASync tags (also known as Enhanced Failover tags). These fields are very helpful for troubleshooting your Enhanced Failover configuration. SCADASync tags contain diagnostic and network information pertaining to your Enhanced Failover configurations. These runtime information fields are available in iFIX 5.1 and greater.

For more information on these runtime information fields, refer to the Runtime Information Fields for Enhanced Failover section.