excess then it will impose a delay or busy state when application 2 accesses the same device or set of devices thus the extra staging also affects concurrency devices or processes concurrently actuating the same resort are said to be in 34 contention 34 this becomes exacerbated when one hdd has failed in a raid 5 array 213 and it is necessary to reconstruct the data from the remaining hdds 211 either for progressively reconstituting a spare hdd brought on line or for satisfying an access request ordinarily the ckd command set indicates that the staging mode to be used is either full track or partial track from dasd to and from subsystem cache 29 or nvs fast write 31 in the ckd format for the ibm 3390 dasd there are 224 logical sectors per ckd logical track the ckd read command specifies a target beginning sector and the number of tracks to be staged up in this invention this ckd command is interpreted by the ramac drawer as consisting of a target sector and a last or final sector suppose the cpu host 1 or 2 sends a ckd ccw requesting to update records 2 3 and 4 on.