How to split igx log into two when both nodes are on same server

If you want to establish a Java option system property for infogix.uniqueServerName that will be distinct for each running jvm.

-Dinfogix.uniqueServerName 
Under WildFly you can modify appserver.properties, 
property WILDFLY_JAVA_OPTIONS and add -Dinfogix.uniqueServerName=%WILDFLY_NODEID%

%WILDFLY_NODEID% is a Microsoft Windows environment variable reference; 
Please add the appropriate dollar-sign-curly-brace thing for Linux.
If you look at a generated start<cfgname>.bat file in wildfly/bin or wildfly2/bin.
you can see that the generated script has an environment variable WILDFLY_NODEID
that is <hostname>-<port> of the cluster node's JVM.
Which yields distinct values for the file names used for logging.

For WebSphere,appserver.properties will contain properties like 
WEBSPHERE_APP_TARGET.
JAVA_OPTIONS.1 and WEBSPHERE_APP_TARGET.JAVA_OPTIONS.2, with default values
to pull corresponding product-level JVM options from IA.properties
as an example.Modify these (either up in appserver.properties or 
down in IA.properties if you want) to include the additional 
system property with a value that makes them unique for log file production.