8.1.1.45 KIX_USER_TRACE

This optional variable defines the type of traces, one trace file per connection or all traces in the same file.

KIX_USER_TRACE=SID represents one trace file per connection. The other value is STD, in this case traces will be in each stdout of server, if the variable is not set to STD is assumed.

When you want to use transaction / command audit tool against multiple homonymous ART servers, SID should be used.