A key associated with each 4KB block of storage that is available in the CICS region. Access to CICS storage is controlled by key-controlled storage protection. When key-controlled protection applies to a storage access, a store operation (write) is permitted only when the storage key matches the access key associated with the request; a fetch (read) is permitted when the keys match or when the fetch-protection bit of the storage key is zero. In most cases, the access key for a storage operation is the PSW key in the current PSW.