Correct: VCDUTL test1 ISOF1_1.DAT; 1 pat_7.dat pat_1.dat
Incorrect: VCDUTL test1 TEST1.PVD pat_7.dat pat_1.dat 

* VCDUTL.EXE does not directly update the volume descriptor set (test1.pvd). 

As a result, if the file size of pat_1.dat is the same or smaller than pat_7.dat, the pat_7.dat part of the disk image will be replaced with pat_1.dat.
To continue emulation

VCDEMU test1

VCDUTL test1 ISOF1_1.DAT;1 pat_7.dat pat_1.dat -f test1.pat

As a result, an update information file (test1.pat) is created.
To execute emulation continuously, start the VCD emulator with the -u option.

VCDEMU test1 -u test1.pat