the present invention provides fast read performance for accessing a file from a multiplicity of files when its corresponding block id is unavailable , by furnishing new file - positioning commands , allowing access to data based on file number , at the same fast locate speed as with block ids , thereby expanding the range of applications that can use certain tape drive systems effectively . the present invention includes both a device architecture for supporting the file oriented positioning and the appending , as well as a software system that can permit easy application access to the device facilities and system components which permit the advantages to accrue without any software application or operator changes , including a robust architecture for navigating residual data , e . g ., for data recovery . the present invention comprises several device command innovations , a relative positioning command , an absolute positioning command , and other commands , e . g ., for sensing current position .