If a scratch tape volume is being allocated to store the primary or backup copy of the object, MVS scratch tape allocation chooses a library-resident tape volume (from an ATLDS or MTL) that is associated with the Tape storage group. If a scratch tape volume is not needed, an existing tape volume that is associated with an Object or Object Backup storage group that is defined in the current SCDS and capable of being mounted and handling the write request is allocated.