Group and backup volumes are volumes that are already assigned to an Object or Object Backup storage group. If you issue a request to write objects to a tape volume that is already assigned to an Object or Object Backup storage group, the tape volume that OAM selects must have sufficient space available to satisfy the request. If no group or backup tape volumes with sufficient space are available to satisfy the request, OAM attempts to select an OAM scratch tape volume with a compatible unit name and data class to accommodate the write request. If no OAM scratch tape volume is available, OAM allocates an MVS scratch tape volume to accommodate the write request.