FIle restructure bastardization

[Don Coleman]

I have a fP file with 16 qualifiers and a total for 51M records spread 
across the qualifiers.  This business functions 24/7 and it presents 
quite a disruption to have them down for any period of time.  Within 
this file are two YESNO flag fields which are always either "Y" or left 
blank.  Rather than attempt to restructure this file which will take 
hours (Windows network) can I copy a modified map file (with everyone 
out of the system) changing the edit on these two fields from YESNO to 
either * or ALLUP?  Will the new map preserve the fields containing the 
"Y" data?  I do realize that this is not the preferred method of 
restructuring a file but you can see where I am going.  Doing so will 
allow me to use various codes in those fields instead of the limitation 
of Y,N, blank and not force me to add additional fields.

Don Coleman