MariaDB Enterprise Server InnoDB Undo Log

The InnoDB undo log is a transaction log used by InnoDB to keep track of multiple row versions for multi-version concurrency control (MVCC). When a row's value changes, InnoDB stores old versions of the row in the Undo Log.

When transactions are committed and the old row versions are no longer necessary, the InnoDB Purge Threads asynchronously delete old row versions from the Undo Log in the background.

When a transaction is rolled back, InnoDB uses the Undo Log to rollback the transaction's changes.

Feature Summary

Feature

Detail

Resources

Transaction Log

InnoDB Undo Log

Storage Engine

InnoDB

Purpose

Multi-Version Concurrency Control (MVCC)

Availability

All ES and CS versions

Location

Quantity

Set by innodb_undo_tablespaces

Size

10 MB per tablespace by default (grows as needed)

Basic Configuration

[mariadb]
...
innodb_undo_tablespaces=8