binlogs

Binlogs, short for binary logs, are a server-side log used by MySQL-compatible database systems to record data-changing events in a binary format. They are a core mechanism for replication, point-in-time recovery, and auditing, and are produced only when binary logging is enabled on the server.

Contents and formats: A binlog contains events that describe changes to data, such as row updates, deletions, and insertions, as well as certain metadata events (for example, log rotation and format description). The exact event types depend on the configured binlog format, which can be statement-based, row-based, or mixed. Binlogs are written to binary log files and tracked by an index file. Each event includes a position offset, which is used to replay changes in the correct order.

Administration and maintenance: Important settings include enabling or disabling binary logging, choosing the binlog format, controlling file size and rotation, and managing retention (for example, via expire_logs_days). Additional options govern replication behavior, such as server-id and whether slave servers should apply updates from the binlog. Rotation creates new binlog files, while old files can be purged once they are no longer needed for recovery or replication.

Usage and limitations: In replication, slaves read the master’s binlog and apply the recorded changes to stay synchronized. For point-in-time recovery, a backup can be restored and binlog events after the backup can be replayed to restore the database to a specific moment. Binlogs mainly record data-modifying statements; non-deterministic statements can pose challenges in statement-based formats, and binlogs require reliable storage and prudent retention strategies to avoid data loss or excessive growth. Binlogs are a key component of MySQL-compatible ecosystems, enabling accurate recovery and consistent replication.