Abstract: A peripheral data storage subsystem has means for responding to a MOUNT command received from a host processor to create and mount a host-processor-addressable logical data-storage volume. Such logical data-storage volume has a serial number VOLSER indicated in the MOUNT command. The logical data volume is assigned a predetermined area of a physical data volume, such area being termed a partition. The illustrated embodiment shows a tape subsystem in which the partitions are accessed by a control using a reel tachometer that identifies segments of the tape. Each partition has a number of the tape segments. Controls and methods are described for initializing the subsystem for effecting the automatic volume creation, appending data into a logical volume, how logical volumes are made to be portable, moving logical volumes amongst diverse physical media, tape formats usable for such logical volumes, data base control of the logical volumes and volume creation processing.

Abstract: An adaptive data transfer channel providing means for a data management access method (AM) to define the channel subsystem data block transfer size and to transfer an extended data block (EDB) by a single channel transfer command to avoid repeated channel command word (CCW) command decode and status presentation operations. The adaptive scheme of this invention is transparent to the user and downwardly compatible with existing data record storage formats because it is independent of the user application program. The host software in the central processing complex (CPC) tests the peripheral data storage device (PDSD) to ensure compatibility with the EDB CCWs before selecting the channel program (CP) to be used for data block transfer in the subchannel. In the EDB format, the PDSD microcode permits the accumulation of logical data blocks (LDBs) from storage to form a single large EDB before transfer to the CPC responsive to a single transfer command.

Abstract: An adaptive data transfer channel providing means for a data management access method (AM) to define the channel subsystem data block transfer size and to transfer an extended data block (EDB) by a single channel transfer command to avoid repeated channel command word (CCW) command decode and status presentation operations. The adaptive scheme of this invention is transparent to the user and downwardly compatible with existing data record storage formats because it is independent of the user application program. The host software in the central processing complex (CPC) tests the peripheral data storage device (PDSD) to ensure compatibility with the EDB CCWs before selecting the channel program (CP) to be used for data block transfer in the subchannel. In the EDB format, the PDSD microcode permits the accumulation of logical data blocks (LDBs) from storage to form a single large EDB before transfer to the CPC responsive to a single transfer command.