There's no mention of Windchill here, although outside of Windchill I'm not sure what they'd be talking about. The OP needs to clarify if they are talking about the same thing.
I'm inclined to agree with Doug Schaefer, we can't be too quick to close out Product Ideas without understanding more of the use case. Zbigniew Danielewski - can you provide more clarity and answer the question of whether this idea also pertains to PTC Windchill?
PTC Windchill developers should disable synchronization between two separate Creo3 sessions.
In Creo2 there was no synchronization between multiple sessions and the user decided which one is to be connected to Windchill (PDMLINK) and in another one could work "standalone", for example with files stored on local disk.
If two Creo3 sessions are automatically synchronized, this situation complicates designer's work, especially on new parts and assemblies. For example, if we have created a new prt or asm (on local disc) and we would like to compare this component with similar component that exists in PDMlink - it is not possible.
This situation very complicates the process of designing.
In my opinion there is no risk regarding data integrity affecting Windchill. Always one server/one workspace is active. In standalone Creo session data files cannot be saved to Windchill.
