Definition
Append every change to a durable log before applying it, so the database can recover after a crash.
How it works
The backbone of durability (the D in ACID): on restart the DB replays the WAL to redo committed work and undo half-done transactions. The same log doubles as the source for replication and change-data-capture. Sequential appends are fast, which is why nearly every storage engine uses one.
Common questions
What is Write-Ahead Log?
Append every change to a durable log before applying it, so the database can recover after a crash.
How does Write-Ahead Log work?
The backbone of durability (the D in ACID): on restart the DB replays the WAL to redo committed work and undo half-done transactions. The same log doubles as the source for replication and change-data-capture. Sequential appends are fast, which is why nearly every storage…
What is Write-Ahead Log used for in system design?
The backbone of durability (the D in ACID): on restart the DB replays the WAL to redo committed work and undo half-done transactions. The same log doubles as the source for replication and change-data-capture. Sequential appends are fast, which is why nearly every storage…