Looks like both "$" and "$$" work in the Filter of Source Transformation. I am not sure what the difference is btween these 2 symbols.
In PowerCenter (which is the technical basis for ICS, not sure about IICS) two dollar signs are used for three different kinds of entity:
- mapping parameters,
- mapping variables,
- workflow variables.
All session parameters start with one single dollar sign. And their naming rules are very strict.
Again, this is PowerCenter, not ICS. It might well be that these rules have been changed for ICS. I don't have the manuals for ICS at hand, so I can't check myself.