The format of the list form of GENCB is:
[label]
GENCB
BLK={ACB|EXLST|RPL} [,AM=VSAM] [,COPIES=abs expression] [,keyword={address|name|abs expression|option},...] [,LENGTH=abs expression] [,LOC={BELOW|ANY}] [,RMODE31={ALL|BUFF|CB|NONE}] ,MF={L|(L,address[,label])} [,WAREA=address]