The redo log is a disk-based data structure used during crash
recovery to correct data written by incomplete transactions.
During normal operations, the redo log encodes requests to change
InnoDB table data that result from SQL
statements or low-level API calls. Modifications that did not
finish updating the data files before an unexpected shutdown are
replayed automatically during initialization, and before the
connections are accepted. For information about the role of the
redo log in crash recovery, see Section 15.18.1, “The InnoDB Recovery Process”.
By default, the redo log is physically represented on disk as a
set of files, named
ib_logfile1. MySQL writes to the redo log
files in a circular fashion. Data in the redo log is encoded in
terms of records affected; this data is collectively referred to
as redo. The passage of data through the redo log is represented
by an ever-increasing LSN value.
For related information, see: