1. A method of executing an instruction to execute a Store Storage Class Memory Information command in a computing environment comprising main storage and storage class memory, said method comprising: obtaining by an input/output (I/O) subsystem a request block, the request block comprising a command code indicating the Store Storage Class Memory Information command; based on the command code, obtaining by the I/O subsystem information relating to the storage class memory; and storing the information in a response block, the response block configured to include a header area and a storage class memory address list of one or more entries representing one or more storage class memory increments that occupy one or more ranges of storage class memory addresses, and wherein the storing the information comprises storing header information in the header area and storing the one or more entries in the response block, wherein the header area includes parameters about the list of one or more entries including an indication of a size of storage class memory increments.