Controlling the resource dictionary in P6

Hello planners

Can anyone tell me what is the current best practice for controlling the resource dictionary when managing a P6 database where many contractors will be supplying updates?  I will set up a complete resource dictionary of labour, plant and materials for the contractors to populate. Some contractors will have direct access to the database & some will be submitting xer files.

In the past I have found that the dictionary quickly fills up with duplicate resources. I want to control the resource dictionary so that any new resources that contractors want to add have to come through me.

Would appreciate hearing from anyone who has been in a similar position using current versions of P6.  The last time I did this was a few years ago & I am hoping it all works better these days.

Your hopefully

Tim Isaac