What is the MySQL binary log (binlog) and what is it used for?
Jun 11, 2025 pm 03:41 PM
MySQL's binary log (binlog) is a binary log that records database change operations, and is used in scenarios such as data recovery, master-slave replication and auditing. 1. Binlog is a logical log file that records all operation events that modify data, such as INSERT, UPDATE, DELETE, etc., but does not include SELECT or SHOW query statements; 2. Its main uses include: data recovery by replaying the log, supporting master-slave replication to achieve data synchronization, and used to analyze operation records to meet audit requirements; 3. To enable binlog, log-bin, server-id, binlog_format and expire_logs_days parameters in the configuration file, and restart MySQL to take effect; 4. You can use SHOW BINARY LOGS and SHOW MASTER STATUS to view log information, and use mysqlbinlog The tool parses the content and can clean old logs by file name or time to free up disk space. Rational configuration and management of binlogs are crucial to ensuring data security.
MySQL's binary log (binlog for short) is an important function of the MySQL server. It records all operations that perform changes to the database (such as INSERT, UPDATE, DELETE, etc.), but does not include SELECT or SHOW query statements. Its main function is to be used in data recovery, master-slave replication, and auditing scenarios.
1. What is Binary Log?
Binary log is a binary format file that records "events" of all changed data in the database. Each event describes the specific content of an operation, such as which table has been modified, which rows have been modified, what statements have been used, etc.
You can understand it as the "operation log" of the database, but it is a log at the logical level, not a physical log like redo log.
After binlog is enabled, MySQL generates a series of log files named in mysql-bin.xxxxxx format and creates a new file every time the log is restarted or manually refreshed.
2. Common uses of Binary Log
- Data recovery : If you accidentally delete a table or delete data by mistake, as long as the binlog is not cleaned up, you can recover the data through it.
- Master-slave Replication : The binlog on the master library will be read and reproduced from the slave library to achieve data synchronization.
- Data Audit : binlog can be analyzed to track the time, source and specific content of certain operations, help troubleshoot problems or meet compliance requirements.
For example, after an error deletion occurs, the DBA can use mysqlbinlog tool to parse the log, find the last correct operation before the error occurs, and then skip the error part for recovery.
3. How to enable and configure Binlog
To enable binlog in MySQL, you need to add the following configuration file (usually my.cnf or my.ini):
[mysqld] server-id=1 log-bin=mysql-bin
Several key parameters descriptions:
-
log-bin: Specifies the prefix of the binlog file name, the default ismysql-bin. -
server-id: for master-slave replication, each server must be unique. -
binlog_format: Set the log format, commonly used values ??areSTATEMENT,ROWandMIXED. -
expire_logs_days: Controls the number of days of log retention to avoid full disk.
After the configuration is completed, restart MySQL will take effect.
4. Viewing and management of Binlog
You can use SHOW BINARY LOGS; see what binlog files are currently in there, or use SHOW MASTER STATUS; see the binlog file currently in its writing.
To view binlog content, you need to use mysqlbinlog command line tool. For example:
mysqlbinlog mysql-bin.000001
This command will output all event contents in the binlog file. You can also add --start-datetime and --stop-datetime parameters to filter operations for a specific period of time.
Additionally, it is important to clean old binlog regularly and can be manually cleaned with the following command:
PURGE BINARY LOGS TO 'mysql-bin.000010'; -- Or clean up PURGE BINARY LOGS BEFORE '2025-04-01 00:00:00';
Basically that's it. Although binlog seems to be just a log file, it plays a very critical role in data security and high availability architecture. Rationally configuring and managing binlog can help you recover your losses at critical moments.
The above is the detailed content of What is the MySQL binary log (binlog) and what is it used for?. For more information, please follow other related articles on the PHP Chinese website!
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