Depending on your configuration and size, you may have (or end up with) more than one storage subsystem in the same disk box. In that case, each subsystem must have a unique SSID. It is possible, however, to have a same SSID in two different boxes, but I don't recommend that.
Commands like PPRC in ICKDSF use SSID, serial number of the box and a two-digit unit address to identify the disk that you want to operate on, so you might have the same SSID as long as the serial numbers are different. But even then, you will want that extra layer of protection in having different SSID's, especially if you acquired the two boxes at the same time, in which case the serial numbers might not differ by much. If you use a unique disk device numbering scheme (meaning one and unique device address for any given physical DASD), then you may indeed use the device address of the first device in the subsystem as a SSID. If all SSID's are like that, then you only have to maintain a small table containing SSID's and serial numbers for use in EXECs, because you will know SSID from the device address. Otherwise, you'll need a table with device addresses (or ranges), SSIDs and serial numbers. Ivica
