All of this revolves around the 12.x Web Viewer CCIClient.properties file, TCPIP.Sysid parameter, or Client System ID. A historical note about this parameter is in order here. It was always (going back to at least 2.0 Web Viewer) a requirement that every Web Viewer Server within a CCI network have a unique CCI Client Identification, System Name, or as it was later known in the Java version CCI, TCPIP.Sysid parameter or Client System ID. The 12.1 ConfigTool calls it the "Client System ID." The way this CCI System Name works is, you either leave the parameter blank (in which case it is populated by the application with a value based on the server machine name, or you manually code your own, unique value.
In shops with multiple servers with long machine names where a unique value is not assured within the first eight characters (longer System Names are truncated at 8 characters internally within the application), manually-coded, unique CCI System Names are required. The bottom line is that it is a requirement that every server within a CCI/Common Services network, have a unique CCI Client Identification, System Name, or TCPIP.Sysid parameter value, or CCI Client System Name.
There is a 12.1 Web Viewer install/configuration scenario where this CCI parameter can confound things. If Web Viewer 12.1 is installed and configured, then deployed to multiple systems with an external configuration, the TCPIP.Sysid= parameter can be propogated to all systems with the same value - as the EAR file is deployed to each additional system, the same, non-unique TCPIP.Sysid= parameter value is propagated. When each system is brought on line and/or users begin to utilize the application, CCI will be unable to identify from which system a particular communication originated.