Question 11888 – UGC NET CS 2014 Dec – paper-3

Write-Ahead Log: When in-place updating is used, it is necessary to use a log for recovery. In this case, the recovery mechanism must ensure that the before image of the data item is recorded in the appropriate log entry and that the log entry is flushed to disk before the before image is overwritten with the after image in the database on disk. This process is generally known as write-ahead logging.
Checkpoint is a mechanism where all the previous logs are removed from the system and stored permanently in a storage disk. Checkpoint declares a point before which the DBMS was inconsistent state, and all the transactions were committed.
Log Buffer: A log buffer is a circular buffer that holds information about changes made to the database.