Data Base Recovery Using Write Ahead Log Protocol
Original Publication Date: 1980-Jan-01
Included in the Prior Art Database: 2005-Feb-13
A method for data base recovery using a write ahead log (WAL) protocol in an Information Management System (IMS) which avoids logging the TRANSACTION UNDO ACTIVITY. The method assumes page locking and physical (page oriented) logging of updates. In this regard, a transaction abort undoes its updates and then enters an "abort" record into the log and forces the log to non-volatile storage. While undoing updates, the Log Sequence Number (LSN) used with the WAL protocol is reset to its pre-update value. By recording the buffer pool page reads and writes in the log, system restart can compute a conservative estimate of the contents of the buffer pool at the time of a crash. System restart distinguishes between transactions which aborted and transactions which were incomplete at the time of the crash.