Intent log
Encyclopedia
An intent log is a mechanism used to make computer
operations more resilient in the event of failures. They are used in database software
, transaction managers, and some file system
s. 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 disk. 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.
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
operations more resilient in the event of failures. They are used in database software
Database Software
Database Software was a software publisher based in Cheshire, England. Software published by the company includes the Red Arrows game for the ZX Spectrum and the office suite Mini Office II, as well as games and educational software for children....
, transaction managers, and some file system
Journaling file system
A journaling file system is a file system that keeps track of the changes that will be made in a journal before committing them to the main file system...
s. In database area, transaction log
Transaction log
In the field of databases in computer science, a transaction log is a history of actions executed by a database management system to guarantee ACID properties over crashes or hardware failures...
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 disk. 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.