There are a couple of things you need to do for using global signals in DC. Firstly there are special symbols of type 'Positive Tap', 'Negative Tap' or 'Ground Tap' which you place in your schematic, there should be some examples in the libraries shipped with DC. Basically the symbol represents a power rail of some kind, to define it the symbol should have a single pin with two properties, Pin Name (it doesn't matter what you call this) and Net Name, this one is important, the Net Name must equal the global signal you wish to use. For example, if you want a global GND signal then the Net Name should be GND on the symbol. Symbol Type in this case would be Ground Tap.
The other part of the 'global' equation is a file called the Global Signals file (see help pages 'install tree'/7.9EE/docs/htmldocs/wwhelp/wwhimpl/js/html/wwhelp.htm?href=dc_olh_ref/dcolh_6th1.html&tab=search&ihub=mgc_ih available from Help, do a search on Global Signal).
This file lists all of the global signals available to the system and has a syntax of:
!Netname Allowed tap rotations Supply Attribute
!------- --------------------- ----------------
AGND FF FF FF FF SUPPLY=GND
CGND FF FF FF FF SUPPLY=GND
GND FF FF FF FF SUPPLY=GND
VBB FF FF FF FF SUPPLY=NEGATIVE
VCC FF FF FF FF SUPPLY=POSITIVE
You will find it in the SDD_HOME\standard\config\vbdc folder, the file is called global. There must be a corresponding entry for every 'tap' symbol you have in your library. Personally I created a number of symbols for various supplies such as +5v, +12V, -12V, GND, AGND etc. each symbol had a corresponidng entry in the global file. The allowed tap rotations section may be left as FF FF FF FF, it has no relevance in Design Capture/DesignView and is a carry over from ACE and ACEPlus (now I'm showing my age :-) ).
Thanks Robert for the suggestion !
I will try to implement it .