First Add the fields whatever you want

then use CHGPF command

Physical file . . . . . . . . . > MyPf

Library . . . . . . . . . . . MyLib

System . . . . . . . . . . . . . *LCL

Source file . . . . . . . . . . MYSourceFile

Library . . . . . . . . . . . MyLib

Update the Physical file.No need to compile again.