Submitting your feedback...
Knowledge Base Article
KB01346 - UniInt Phase II Failover Scenarios
Product: PI Interfaces / UNIINT
Version(s): 4.5+
 

Issue

There are many possible scenarios for Phase II UniInt Failover. This behavior can be a bit mysterious at times. What should be the expected end result in each possible failover situation? The following scenarios were tested:
 
  • Scenario I : IF1 loses connection to DS1
  • Scenario II : IF1 loses connection to DS1 and IF2 loses connection to DS2
  • Scenario III : IF2 loses connection to DS2
  • Scenario IV : IF2 loses connection to DS2 and IF1 loses connection to PI1
  • Scenario V : IF1 loses connection to PI1 and IF2 loses connection to PI2
  • Scenario VI : IF1 loses connection to PI1, IF2 loses connection to PI2, both interfaces lose connection to shared file ("Double Blind")
  • Scenario VII : IF1 loses connection to PI1 and IF1 loses connection to shared file ("IF1 Single Blind")*
  • Scenario VIII : IF2 loses connection to PI2 and IF2 loses connection to shared file ("IF2 Single Blind")*

Solution

IF1 is the acting primary with IF2 in a good backup state at the start of each trial. 

The following legend applies to all scenarios:

IF Interface
DS Data source
PI PI Data Archive
Share Shared failover file
 
 

Scenario I

st-widget-{image: ScenarioI.gif}
Result: IF II becomes acting primary.
 

Scenario II

st-widget-{image: ScenarioII.gif}
Result: IF II becomes primary with communication error to PI.
 

Scenario III

st-widget-{image: ScenarioIII.gif}
Result: IF I remains primary and backup has communication error to data source.
 

Scenario IV

st-widget-{image: ScenarioIV.gif}
Result: IF I remains primary; backup has communication error to data source.
 

Scenario V

st-widget-{image: ScenarioV.gif}
Result: IF I remains primary regardless of the setting "Do not failover if both interfaces lose connection to PI server" (DNFBPI).
 

Scenario VI

st-widget-{image: ScenarioVI.gif}
Result: IF I will remain primary with "Primary Error" state. IF II will remain backup with "Backup Error" state. Data loss possible if IF I then loses connection to data source.
 

Scenario VII

st-widget-{image: ScenarioVII.gif}
Result: IF I will be in "Primary Error" state and will buffer data. At the same time, IF II will also transition to acting primary and function normally. Once IF I reestablishes communication to PI server, duplicate data stored in the buffer will be sent.
 

Scenario VIII

st-widget-{image: ScenarioVIII.gif}
Result: IF I will remain acting primary and behave as normal. IF II will transition to "Backup Error" state. Possible data loss situation if IF I then loses connection to data source.
 

Background

All scenarios were tested under the following conditions:
Interface: PI OPC DA Interface
Version: 2.5.1.3
UniInt: 4.5.5.11
Failover Mode: Phase II, Hot
Starting condition: All connections are good. IF1 is acting primary with IF2 in a good backup state.
 
Article ID: KB01346 Created: 2016-02-10
Article Type: Informational Last Updated: 2016-02-10