RECOVERABILITY IN MASS STORAGE DATA BASE SYSTEMS

摘要

The message management system utilizes a flat file (20) on mirrored disk for storing fixed-length Message Segments (MS) of variable-length Messages to be managed by the system. Inconsistencies between mirrored copies of data are tolerated and cor- rected. Message Management includes Storing, Retrieving and Deleting Message s in response to commands from clients. Each Message Segment in the flat file is stored in a record containing the Messag e Segment data and Recovery Information (RI). A data base (21) for accessing the Message Segments in the flat file is maintained on system disk. The Recovery Information is such as to permit recovery of the data base from the Recovery Information in the flat file if the data base is obsolete, lost or corrupted. TNAUDIT file is utilized to determine that the data base is synchronized wit h the flat file. If data base inconsistency is detected, the data base is rebuilt from the Recovery Information.