Abstract: A data storage and retrieval system which includes encoded information regarding known valid system configurations, nominal performance specifications for various I/O devices, and nominal performance specifications for various interconnecting communication buses. A method to validate the apparent configuration of Applicants' system. A method to evaluate the performance of each I/O device and interconnecting bus disposed within Applicants' system.

Abstract: 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.