transaction log file

A file that contains a record of the changes that were made to an Exchange database. All changes to the database are recorded in the transaction log files before they are written into the database files. If a database shuts down unexpectedly, unfinished transactions can be restored by replaying the transaction log files into the database. [Exchange 2007]

A file that provides fault tolerance in the event that data needs to be restored to the information store or directory databases. [Exchange 5.5]