Write-ahead logging

The so-called write ahead logging (WAL ) is a method of database technology that contributes to guarantee the atomicity and durability of transactions. It states that modifications before the actual writing ( introduction into the database) must be logged.

By the WAL principle is a so-called " update -in-place " -that is, the old version of a record is overwritten by the new version in the same place. This has the particular advantage that index structures for change operations do not need to be updated with, because the changed records are still to be found in the same place. The previous logging a change is needed to ensure the repeatability of the change in the event of an error.

• Databases