Abstract: Functions MINBUFLSN and LOWTRANLSN, implemented in a computerized routine, are defined and comprise first and second components of a checkpoint. MINBUFLSN is functionally related to a first update to a first of "dirty" data pages in the RAM buffer. LOWTRANLSN is functionally related to the earliest update of a sequence in a transaction table wherein each update corresponds to an uncommitted transaction. The two components are derived during write-ahead logging and stored in the log header periodically as a function of logging activity. Upon recovery, the checkpoint is retrieved and a functional comparison between the components thereof employed in the recovery algorithm. The conventional analysis pass of the recovery log is avoided and a reduced overhead during logging is provided as well as an efficient recovery.

Abstract: Method for reducing data loss during I/O errors and power failure during non-atomic writes to media in a transaction management system using write-ahead logging protocol. A recovery log is written during forward processing. On system restart processing, the log is traversed and a REDO executed. Recovery is effected from detected incomplete log writes or log write failures and uncommitted transactions are undone. A technique is provided in which files having I/O errors are identified, whereby subsequent restart operations are prevented from accessing these files. In one embodiment index files with such error are renamed, serving to indicate that corresponding original files contain errors, and the error index files are automatically rebuilt whereby I/O error on the files causes no data loss. The index file rebuild does not invalidate access plans related to the failed index.