What information is recorded in the WAL log in the context of databases?

The WAL (Write-Ahead Logging) journal in databases is used to ensure data reliability and recovery after failures. It records information about all changes that will be made to the database, before these changes are applied to the main data files.

This includes:

• insert, update, and delete operations;
• transaction information (start, commit, rollback);
• data necessary for restoring the database state after a crash.

Thus, in case of a failure, the system can use WAL records to rollback or reapply transactions, ensuring data integrity and consistency.