# Writing Logs Into Tables

By default, all logs are disabled or written into files. The [general query log](https://mariadb.com/docs/server/server-management/server-monitoring-logs/general-query-log) and the [slow query log](https://mariadb.com/docs/server/server-management/server-monitoring-logs/slow-query-log) can also be written to special tables in the `mysql` database. During the startup, entries will always be written into files.

Note that [EXPLAIN output](https://mariadb.com/docs/server/server-management/server-monitoring-logs/slow-query-log/explain-in-the-slow-query-log) will only be recorded if the slow query log is written to a file and not to a table.

To write logs into tables, the [log\_output](https://mariadb.com/docs/server/variables-and-modes/server-system-variables#log_output) server system variable is used. Allowed values are `FILE`, `TABLE` and `NONE`. It is possible to specify multiple values, separated with commas, to write the logs into both tables and files. `NONE` disables logging and has precedence over the other values.

So, to write logs into tables, one of the following settings can be used:

```sql
SET GLOBAL log_output = 'TABLE';
SET GLOBAL log_output = 'FILE,TABLE';
```

The general log will be written into the [general\_log](https://mariadb.com/docs/server/reference/system-tables/the-mysql-database-tables/mysqlgeneral_log-table) table, and the slow query log will be written into the [slow\_log](https://mariadb.com/docs/server/reference/system-tables/the-mysql-database-tables/mysql-slow_log-table) table. Only a limited set of operations are supported for those special tables. For example, direct DML statements (like `INSERT`) on those tables will fail with an error similar to the following:

```sql
ERROR 1556 (HY000): You can't use locks with log tables.
```

To flush data to the tables, use [FLUSH TABLES](https://mariadb.com/docs/server/reference/sql-statements/administrative-sql-statements/flush-commands/flush) instead of [FLUSH LOGS](https://mariadb.com/docs/server/reference/sql-statements/administrative-sql-statements/flush-commands/flush).

To empty the contents of the log tables, [TRUNCATE TABLE](https://mariadb.com/docs/server/reference/sql-statements/table-statements/truncate-table) can be used.

The log tables use the [CSV](https://mariadb.com/docs/server/server-usage/storage-engines/csv) storage engine by default. This allows an external program to read the files if needed: normal CSV files are stored in the `mysql` subdirectory, in the data dir. However that engine is slow because it does not support indexes, so you can convert the tables to [MyISAM](https://mariadb.com/docs/server/server-usage/storage-engines/myisam-storage-engine) (but not other storage engines). To do so, first temporarily disable logging:

```sql
SET GLOBAL general_log = 'OFF';
ALTER TABLE mysql.general_log ENGINE = MyISAM;
ALTER TABLE mysql.slow_log ENGINE = MyISAM;
SET GLOBAL general_log = @old_log_state;
```

[CHECK TABLE](https://mariadb.com/docs/server/reference/sql-statements/table-statements/check-table) and [CHECKSUM TABLE](https://mariadb.com/docs/server/reference/sql-statements/table-statements/checksum-table) are supported.

[CREATE TABLE](https://mariadb.com/docs/server/server-usage/tables/create-table) is supported. [ALTER TABLE](https://mariadb.com/docs/server/reference/sql-statements/data-definition/alter/alter-table), [RENAME TABLE](https://mariadb.com/docs/server/reference/sql-statements/data-definition/rename-table) and [DROP TABLE](https://mariadb.com/docs/server/server-usage/tables/drop-table) are supported when logging is disabled, but log tables cannot be partitioned.

Contents of log tables are not logged in the [binary log](https://mariadb.com/docs/server/server-management/server-monitoring-logs/binary-log), thus cannot be replicated.

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