Sughrue, Mion, Zinn, Macpeak & Seas
Control unit for controlling reading and writing of a magnetic tape unit
 The control unit for the magnetic tape unit compresses data and writes in a physical block unit in the buffer according to the data write instruction from the host computer or without compressing writes in a logical block unit in the buffer. And, according to the data read instruction from the host computer, the data read from the magnetic tape unit is stored in the buffer and transferred to the host computer. When the read data is an extended format due to compression, the data is expanded before being transferred. When an error occurs in writing data in the magnetic tape unit, information such as the maximum block size and total capacity of data within the buffer is informed to the host computer. In the following data recovery process, the unwritten data within the buffer is recovered in the logical block unit or physical block unit. In the recovery in the logical block unit, when it is the standard format data, it is read as it is and transferred to the host computer. When it is the extended format due to compression, it is read after effecting expansion processing. In the recovery in the physical block unit, the data is not expanded and read to be recovered in the compressed data. 
NEC Corporation
G G G G
G06F G11B G11B G06F
inventional inventional inventional additional
Yoshiaki
Mori