You can use the DEVSERV PATHS command to display the number of configured cylinders for a device or range of devices under CYL header. If a device is part of a DUAL COPY pair (devices behind a 3990-3 or older), then the ALT dddd is displayed under the CYL header. The first character of the UNIT number represents the subchannel set number.
18.09.58 SYSTEM1 ds p,0f4a,4
18.09.58 SYSTEM1 IEE459I 18.09.58 DEVSERV PATHS 600
UNIT DTYPE M CNT VOLSER CHPID=PATH STATUS
RTYPE SSID CFW TC DFW PIN DC-STATE CCA DDC CYL CU-TYPE
00F4A,33909 ,O,000,EV9LIA,00=+ 04=+
2105 201F Y YY. YY. N SIMPLEX 3A 10017 2105
************************ SYMBOL DEFINITIONS ***************************
O = ONLINE + = PATH AVAILABLE