Write-Ahead Logging (WAL) is a technique used in database management systems (DBMS) to ensure the durability of transactions and recoverability of data in the event of system failures or crashes. With WAL, modifications to the database are first written to a log file on disk before being applied to the database itself. This log file records the changes made by transactions in a sequential manner, ensuring that all changes are logged before they are applied to the database. By writing changes to the log file before modifying the actual database, WAL provides a reliable mechanism for recovering transactions in the event of a crash. During recovery, the system can replay the logged transactions from the log file to restore the database to a consistent state. Write-ahead logging is a critical component of many DBMS systems and is essential for ensuring data durability and recoverability. s://en.wikipedia.org/wiki/Write-ahead_logging