It's difficult to advise you without knowing what the code is doing inside those while loops, but in your position I would try and avoid using them completely, and do something more like this:

awk '
        /^RX SYSTEM/ { section=$3 }
        section=="CFO" {
                print "processing CFO stuff: " $0
        }
        section=="DAX" {
                print "processing DAX stuff: " $0
        }
        section=="TC" {
                print "processing TC stuff: " $0
        }
' inputfile > outputfile