An intent log is a mechanism used to make
computer
A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...
operations more resilient in the event of failures. They are used in
database software, transaction managers, and
some file systems. In database area,
transaction log is widely used. In file system area, intent log is used more often.
Before performing an operation, a record of the intent to perform it is written, usually to some relatively permanent medium such as a
hard disk drive. After the operation is performed, another record is written. Usually, an operation will change some data in a system. In some cases, the intent record will contain a copy of the data before and after the operation.
This adds overhead, sometimes a significant amount. Enough data is written to the log to either redo or to undo the operation later.
If a failure occurs, then when the system is recovering, it can use the intent log to detect what operations were still in process during the failure, and use the intent log to help recover from the failure, usually by either undoing a partially completed operation, or by redoing one that might need to be completed.
See also
*
Journaling file system
*
Write-ahead logging
References
{{Reflist
Transaction processing