Each database must have at least one log file. The log file contains the transaction log records of all changes made in a database (for more information on what is contained in the transaction log, see Chapter 27, “Transaction Management and the Transaction Log”). By default, log files have the file extension
A database can have several log files, and each log file can have a maximum size of 32TB. A log file cannot be part of a filegroup. No information other than transaction log records can be written to a log file.
For more information on the log file and log file management, see Chapter 27.