Emulating the S/390 read backwards tape operation on SCSI attached tape devices
AssigneeInternational Business Machines Corporation
InventorCarmine Castaldo, Jr.
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Abstract
Disclosed is a method for attaching SCSI tape devices which may only read in a forward direction to an S/390 compatible computer system. This involves translating S/390 I/O operations for channel communication by emulating an S/390 "Read Backwards" channel command with a single "Read Backwards" routine to be used for all SCSI tape drives regardless of read capabilities in the backward direction. The emulation of a S/390 "Read Backwards" channel command includes using a combination of existing tape positioning commands, including: the RF (Read Forward) command, parsing technique to obtain the appropriate bytes to be stored into memory, and calculation for the residual byte count.
Claims5
A method for attaching SCSI tape devices which can only read in a forward direction to an S/390 compatible computer system, comprising the steps of:
- translating S/390 operations for channel communication by emulating an S/390 "Read Backwards" channel command with a single "Read Backwards" routine capable of operating SCSI tape drives that read only in the forward direction and SCSI tape drives that read in the forward direction and in the backward direction.
Dependencies are inferred from the claim text.