Importance

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Abstract

The present invention is made such that data in a buffer can be transferred even when read back commands are continuously issued so as to completely eliminate the need for a mechanical operation required for each data block in ROR processing, resulting in considerably reducing a processing time. For this purpose, a method of controlling a magnetic tape unit of the present invention includes the steps of, when the read back command is received from a host processor, reading plurality of data blocks, when a read position of an MTU meets a predetermined condition, reading in a forward direction a plurality of data blocks in the range between the position and a start position of the read back command so as to write the data blocks into the data buffer, storing read commands concerning the data blocks into a command queue in reverse order to how the data blocks are read, and thereafter, in response to a read command from the host processor, reading the data blocks in the data buffer in the order in which the read commands are arranged in the command queue so as to transfer the data blocks to the host processor after data expansion. Further, the invention is applied to a magnetic tape unit to write data compressed through, for example, an EDRC system onto a magnetic tape, and read the compressed data therefrom.

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First Claim