Selecting General Query Log and Slow Query Log Output Destinations MySQL Server has several logs that can help you find out what activity is taking place. By default, no logs are enabled, except the error log on Windows. (The DDL log is always created when required, and has no user-configurable options; see The DDL Log.) The following log-specific sections provide information about the server options that enable logging. By default, the server writes files for all enabled logs in the data directory. You can force the server to close and reopen the log files (or in some cases switch to a new log file) by flushing the logs. Log flushing occurs when you issue a  FLUSH LOGS  statement; execute  mysqladmin  with a  flush-logs or  refresh  argument; or execute  mysqldump  with a  --flush-logs  or  --master-data  option. See Section 13.7.8.3, “FLUSH Statement” , Section 4.5.2, “mysqladmin — A MySQL Server Administration Program” , and Section 4.5.4, “mysqldump — A Database Backup Program” . In addition, the binary log is flushed when its size reaches the value of the  max_binlog_size  system variable. You can control the general query and slow query logs during runtime. You can enable or disable logging, or change the log file name. You can tell the server to write general query and slow query entries to log tables, log files, or both. For details, see Section 5.4.1, “Selecting General Query Log and Slow Query Log Output Destinations” , Section 5.4.3, “The General Query Log” , and Section 5.4.5, “The Slow Query Log” . The relay log is used only on replicas, to hold data changes from the replication source server that must also be made on the replica. For discussion of relay log contents and configuration, see Section 17.2.4.1, “The Relay Log” . For information about log maintenance operations such as expiration of old log files, see Section 5.4.6, “Server Log Maintenance” . For information about keeping logs secure, see Section 6.1.2.3, “Passwords and Logging” . MySQL Server provides flexible control over the destination of output written to the general query log and the slow query log, if those logs are enabled. Possible destinations for log entries are log files or the general_log  and  slow_log  tables in the  mysql  system database. File output, table output, or both can be selected. 1022 •Log Control at Server Startup •Log Control at Runtime •Log Table Benefits and Characteristics 5.4.1 Selecting General Query Log and Slow Query Log Output Destinations Log Type Information Written to Log Error log Problems encountered starting, running, or stopping mysqld General query log Established client connections and statements received from clients Binary log Statements that change data (also used for replication) Relay log Data changes received from a replication source server Slow query log Queries that took more than  long_query_time seconds to execute DDL log (metadata log) Metadata operations performed by DDL statements