Method and apparatus for controlling data writing in magnetic recording subsystem

DETAILED DESCRIPTION The present invention is applicable to a magnetic tape subsystem comprising a channel unit, a magnetic tape control unit having a data buffer for temporarily storing blocks of data transferred from the channel unit, and a plurality of magnetic tape units connected to the magnetic tape control unit.
When the data are stored into the data buffer block numbers are assigned to the respective blocks, and when they are read from the data buffer and written into a designated magnetic tape unit, the block numbers are checked before the data blocks are written into the magnetic tape unit.
In accordance with the present invention, the data transferred from the channel unit for writing into the designated magnetic tape unit is assigned with block numbers for the respective data blocks, and then they are stored in the data buffer.
When the data is to be written into the magnetic tape unit, the block number of the data block to be written and the data block number read from the buffer are compared in order to assure exact writing of the data into the designated magnetic tape unit.