Is there a limitation on the number of UV  phantom processes that can run simultaneously on a Windows platform? 

I seem to recall there is but I can't find any documentation for it.

Thanks in advance.

Gil,

As long as you are talking phantoms and not i-pantoms, look at NUSERS setting,  the following document describes it, and has a example about how to calculate. 

UniVerse 11 and Beyond Version 1.3 What You Need to Know Before You Upgrade

It also shows some error messages you may get if not configured correctly.

My NUSERS are set at 256, but I am only able to start 116 phantom jobs. All of these phantoms are logged in the &PH& folder. When I EXECUTE the 117th PHANTOM the &PH& record is blank. No errors displayed or included in the &PH& record. I was expecting an error message when I started the last phantom job. Am I bumping into some other system limit??

My programs I used for testing are below.

I have 1 program to start 117 phantoms, and the 2nd program outputs info about the specific Phantom job:

>ED BP START.PHANTOMS TEST.PHANTOM2

SELECTed record name = "START.PHANTOMS".
6 lines long.

----: P
0001:       MAX = 117
0002:       FOR I = 1 TO MAX
0003:          PRINT I:'/':MAX
0004:          EXECUTE 'PHANTOM TEST.PHANTOM2 -':I
0005:       NEXT I
0006:    END
Bottom at line 6.
----: N

SELECTed record name = "TEST.PHANTOM2".
9 lines long.

----: P
0001: PH.NBR = FIELD(@SENTENCE, '-', 2)
0002: CRT PH.NBR
0003: CRT '@USERNO: ':@USERNO
0004: RETURN.CODE = USERINFO(2, @USERNO, OUTPUT)
0005: CRT 'PID: ':OUTPUT<1, 3>
0006: CRT 'Sleeping for 60 seconds: ':TIME()
0007: SLEEP 60
0008: CRT 'Awake and exiting program: ':TIME()
0009: END
Bottom at line 9.