17.1.4.4 Binary Log Options and Variables

• Startup Options Used with Binary Logging

• System Variables Used with Binary Logging

You can use the mysqld options and system variables that are described in this section to affect the operation of the binary log as well as to control which statements are written to the binary log. For additional information about the binary log, see Section 5.4.4, “The Binary Log”. For additional information about using MySQL server options and system variables, see Section 5.1.6, “Server Command Options”, and Section 5.1.7, “Server System Variables”.

Startup Options Used with Binary Logging

The following list describes startup options for enabling and configuring the binary log. System variables used with binary logging are discussed later in this section.

• --binlog-row-event-max-size=N

  Property	Value
  Command-Line Format	--binlog-row-event-max-size=#
  Type	Integer
  Default Value (64-bit platforms, >= 5.6.6)	8192
  Default Value (64-bit platforms, <= 5.6.5)	1024
  Default Value (32-bit platforms, >= 5.6.6)	8192
  Default Value (32-bit platforms, <= 5.6.5)	1024
  Minimum Value	256
  Maximum Value (64-bit platforms)	18446744073709551615
  Maximum Value (32-bit platforms)	4294967295

  Specify the maximum size of a row-based binary log event, in bytes. Rows are grouped into events smaller than this size if possible. The value should be a multiple of 256. See Section 17.1.2, “Replication Formats”.

• --log-bin[=base_name]

  Property	Value
  Command-Line Format	--log-bin=file_name
  Type	File name

  Enables binary logging. With binary logging enabled, the server logs all statements that change data to the binary log, which is used for backup and replication. The binary log is a sequence of files with a base name and numeric extension. For information on the format and management of the binary log, see Section 5.4.4, “The Binary Log”.

  The option value, if given, is the base name for the log sequence. The server creates binary log files in sequence by adding a numeric suffix to the base name. It is recommended that you specify a base name (see Section B.4.7, “Known Issues in MySQL”, for the reason). Otherwise, MySQL uses host_name-bin as the base name.

  If you supply a value for the --log-bin option, the value is used as the base name for the log sequence. The server creates binary log files in sequence by adding a numeric suffix to the base name. In MySQL 5.6, the default base name is the name of the process ID file, with the suffix -bin. That name can be set with the --pid-file option, and it defaults to the name of the host machine. It is recommended that you specify a base name using the --log-bin option, so that you can continue to use the same binary log file names regardless of changes to the default name.

  The default location for binary log files is the data directory. You can use the --log-bin option to specify an alternative location, by adding a leading absolute path name to the base name to specify a different directory. When the server reads an entry from the binary log index file, which tracks the binary log files that have been used, it checks whether the entry contains a relative path. If it does, the relative part of the path is replaced with the absolute path set using the --log-bin option. An absolute path recorded in the binary log index file remains unchanged; in such a case, the index file must be edited manually to enable a new path or paths to be used. (Previous to MySQL 5.6.5, this did not apply, and manual intervention was required whenever relocating the binary log or relay log files.) (Bug #11745230, Bug #12133)

  Setting this option causes the log_bin system variable to be set to ON (or 1), and not to the base name. Beginning with MySQL 5.6.2, the binary log file base name and any specified path are available as the log_bin_basename system variable.

• --log-bin-index[=file_name]

  Property	Value
  Command-Line Format	--log-bin-index=file_name
  System Variable (>= 5.6.4)	log_bin_index
  Scope (>= 5.6.4)	Global
  Dynamic (>= 5.6.4)	No
  Type	File name

  The name for the binary log index file, which contains the names of the binary log files. By default, it has the same location and base name as the value specified for the binary log files using the --log-bin option, plus the extension .index. If you do not specify --log-bin, the default binary log index file name is binlog.index. If you omit the file name and do not specify one with --log-bin, the default binary log index file name is host_name-bin.index, using the name of the host machine.

  For information on the format and management of the binary log, see Section 5.4.4, “The Binary Log”.

Statement selection options.  The options in the following list affect which statements are written to the binary log, and thus sent by a replication master server to its slaves. There are also options for slave servers that control which statements received from the master should be executed or ignored. For details, see Section 17.1.4.3, “Replication Slave Options and Variables”.

• --binlog-do-db=db_name

  Property	Value
  Command-Line Format	--binlog-do-db=name
  Type	String

  This option affects binary logging in a manner similar to the way that --replicate-do-db affects replication.

  The effects of this option depend on whether the statement-based or row-based logging format is in use, in the same way that the effects of --replicate-do-db depend on whether statement-based or row-based replication is in use. You should keep in mind that the format used to log a given statement may not necessarily be the same as that indicated by the value of binlog_format. For example, DDL statements such as CREATE TABLE and ALTER TABLE are always logged as statements, without regard to the logging format in effect, so the following statement-based rules for --binlog-do-db always apply in determining whether or not the statement is logged.

  Statement-based logging.  Only those statements are written to the binary log where the default database (that is, the one selected by USE) is db_name. To specify more than one database, use this option multiple times, once for each database; however, doing so does not cause cross-database statements such as UPDATE some_db.some_table SET foo='bar' to be logged while a different database (or no database) is selected.

  Warning

  To specify multiple databases you must use multiple instances of this option. Because database names can contain commas, the list will be treated as the name of a single database if you supply a comma-separated list.

  An example of what does not work as you might expect when using statement-based logging: If the server is started with --binlog-do-db=sales and you issue the following statements, the UPDATE statement is not logged:

  USE prices;
  UPDATE sales.january SET amount=amount+1000;

  The main reason for this “just check the default database” behavior is that it is difficult from the statement alone to know whether it should be replicated (for example, if you are using multiple-table DELETE statements or multiple-table UPDATE statements that act across multiple databases). It is also faster to check only the default database rather than all databases if there is no need.

  Another case which may not be self-evident occurs when a given database is replicated even though it was not specified when setting the option. If the server is started with --binlog-do-db=sales, the following UPDATE statement is logged even though prices was not included when setting --binlog-do-db:

  USE sales;
  UPDATE prices.discounts SET percentage = percentage + 10;

  Because sales is the default database when the UPDATE statement is issued, the UPDATE is logged.

  Row-based logging.  Logging is restricted to database db_name. Only changes to tables belonging to db_name are logged; the default database has no effect on this. Suppose that the server is started with --binlog-do-db=sales and row-based logging is in effect, and then the following statements are executed:

  USE prices;
  UPDATE sales.february SET amount=amount+100;

  The changes to the february table in the sales database are logged in accordance with the UPDATE statement; this occurs whether or not the USE statement was issued. However, when using the row-based logging format and --binlog-do-db=sales, changes made by the following UPDATE are not logged:

  USE prices;
  UPDATE prices.march SET amount=amount-25;

  Even if the USE prices statement were changed to USE sales, the UPDATE statement's effects would still not be written to the binary log.

  Another important difference in --binlog-do-db handling for statement-based logging as opposed to the row-based logging occurs with regard to statements that refer to multiple databases. Suppose that the server is started with --binlog-do-db=db1, and the following statements are executed:

  USE db1;
  UPDATE db1.table1 SET col1 = 10, db2.table2 SET col2 = 20;

  If you are using statement-based logging, the updates to both tables are written to the binary log. However, when using the row-based format, only the changes to table1 are logged; table2 is in a different database, so it is not changed by the UPDATE. Now suppose that, instead of the USE db1 statement, a USE db4 statement had been used:

  USE db4;
  UPDATE db1.table1 SET col1 = 10, db2.table2 SET col2 = 20;

  In this case, the UPDATE statement is not written to the binary log when using statement-based logging. However, when using row-based logging, the change to table1 is logged, but not that to table2—in other words, only changes to tables in the database named by --binlog-do-db are logged, and the choice of default database has no effect on this behavior.

• --binlog-ignore-db=db_name

  Property	Value
  Command-Line Format	--binlog-ignore-db=name
  Type	String

  This option affects binary logging in a manner similar to the way that --replicate-ignore-db affects replication.

  The effects of this option depend on whether the statement-based or row-based logging format is in use, in the same way that the effects of --replicate-ignore-db depend on whether statement-based or row-based replication is in use. You should keep in mind that the format used to log a given statement may not necessarily be the same as that indicated by the value of binlog_format. For example, DDL statements such as CREATE TABLE and ALTER TABLE are always logged as statements, without regard to the logging format in effect, so the following statement-based rules for --binlog-ignore-db always apply in determining whether or not the statement is logged.

  Statement-based logging.  Tells the server to not log any statement where the default database (that is, the one selected by USE) is db_name.

  Prior to MySQL 5.6.12, this option caused any statements containing fully qualified table names not to be logged if there was no default database specified (that is, when SELECT DATABASE() returned NULL). In MySQL 5.6.12 and higher, when there is no default database, no --binlog-ignore-db options are applied, and such statements are always logged. (Bug #11829838, Bug #60188)

  Row-based format.  Tells the server not to log updates to any tables in the database db_name. The current database has no effect.

  When using statement-based logging, the following example does not work as you might expect. Suppose that the server is started with --binlog-ignore-db=sales and you issue the following statements:

  USE prices;
  UPDATE sales.january SET amount=amount+1000;

  The UPDATE statement is logged in such a case because --binlog-ignore-db applies only to the default database (determined by the USE statement). Because the sales database was specified explicitly in the statement, the statement has not been filtered. However, when using row-based logging, the UPDATE statement's effects are not written to the binary log, which means that no changes to the sales.january table are logged; in this instance, --binlog-ignore-db=sales causes all changes made to tables in the master's copy of the sales database to be ignored for purposes of binary logging.

  To specify more than one database to ignore, use this option multiple times, once for each database. Because database names can contain commas, the list will be treated as the name of a single database if you supply a comma-separated list.

  You should not use this option if you are using cross-database updates and you do not want these updates to be logged.

Checksum options.  Beginning with MySQL 5.6.2, MySQL supports reading and writing of binary log checksums. These are enabled using the two options listed here:

• --binlog-checksum={NONE|CRC32}

  Property	Value
  Command-Line Format	--binlog-checksum=type
  Introduced	5.6.2
  Type	String
  Default Value (>= 5.6.6)	CRC32
  Default Value (<= 5.6.5)	NONE
  Valid Values	NONE CRC32

  Enabling this option causes the master to write checksums for events written to the binary log. Set to NONE to disable, or the name of the algorithm to be used for generating checksums; currently, only CRC32 checksums are supported. As of MySQL 5.6.6, CRC32 is the default.

To control reading of checksums by the slave (from the relay log), use the --slave-sql-verify-checksum option.

Testing and debugging options.  The following binary log options are used in replication testing and debugging. They are not intended for use in normal operations.

• --max-binlog-dump-events=N

  Property	Value
  Command-Line Format	--max-binlog-dump-events=#
  Type	Integer
  Default Value	0

  This option is used internally by the MySQL test suite for replication testing and debugging.

• --sporadic-binlog-dump-fail

  Property	Value
  Command-Line Format	--sporadic-binlog-dump-fail[={OFF|ON}]
  Type	Boolean
  Default Value	OFF

  This option is used internally by the MySQL test suite for replication testing and debugging.

System Variables Used with Binary Logging

The following list describes system variables for controlling binary logging. They can be set at server startup and some of them can be changed at runtime using SET. Server options used to control binary logging are listed earlier in this section.

• binlog_cache_size

  Property	Value
  Command-Line Format	--binlog-cache-size=#
  System Variable	binlog_cache_size
  Scope	Global
  Dynamic	Yes
  Type	Integer
  Default Value	32768
  Minimum Value	4096
  Maximum Value (64-bit platforms)	18446744073709551615
  Maximum Value (32-bit platforms)	4294967295

  The size of the cache to hold changes to the binary log during a transaction. A binary log cache is allocated for each client if the server supports any transactional storage engines and if the server has the binary log enabled (--log-bin option). If you often use large transactions, you can increase this cache size to get better performance. The Binlog_cache_use and Binlog_cache_disk_use status variables can be useful for tuning the size of this variable. See Section 5.4.4, “The Binary Log”.

  binlog_cache_size sets the size for the transaction cache only; the size of the statement cache is governed by the binlog_stmt_cache_size system variable.

• binlog_checksum

  Property	Value
  Command-Line Format	--binlog-checksum=name
  Introduced	5.6.2
  System Variable	binlog_checksum
  Scope	Global
  Dynamic	Yes
  Type	String
  Default Value (>= 5.6.6)	CRC32
  Default Value (<= 5.6.5)	NONE
  Valid Values	NONE CRC32

  When enabled, this variable causes the master to write a checksum for each event in the binary log. binlog_checksum supports the values NONE (disabled) and CRC32. The default is CRC32 as of MySQL 5.6.6, NONE before that.

  When binlog_checksum is disabled (value NONE), the server verifies that it is writing only complete events to the binary log by writing and checking the event length (rather than a checksum) for each event.

  Changing the value of this variable causes the binary log to be rotated; checksums are always written to an entire binary log file, and never to only part of one.

  In MySQL 5.6.6 and higher, setting this variable on the master to a value unrecognized by the slave causes the slave to set its own binlog_checksum value to NONE, and to stop replication with an error. (Bug #13553750, Bug #61096) If backward compatibility with older slaves is a concern, you may want to set the value explicitly to NONE.

• binlog_direct_non_transactional_updates

  Property	Value
  Command-Line Format	--binlog-direct-non-transactional-updates[={OFF|ON}]
  System Variable	binlog_direct_non_transactional_updates
  Scope	Global, Session
  Dynamic	Yes
  Type	Boolean
  Default Value	OFF

  Due to concurrency issues, a slave can become inconsistent when a transaction contains updates to both transactional and nontransactional tables. MySQL tries to preserve causality among these statements by writing nontransactional statements to the transaction cache, which is flushed upon commit. However, problems arise when modifications done to nontransactional tables on behalf of a transaction become immediately visible to other connections because these changes may not be written immediately into the binary log.

  The binlog_direct_non_transactional_updates variable offers one possible workaround to this issue. By default, this variable is disabled. Enabling binlog_direct_non_transactional_updates causes updates to nontransactional tables to be written directly to the binary log, rather than to the transaction cache.

  binlog_direct_non_transactional_updates works only for statements that are replicated using the statement-based binary logging format; that is, it works only when the value of binlog_format is STATEMENT, or when binlog_format is MIXED and a given statement is being replicated using the statement-based format. This variable has no effect when the binary log format is ROW, or when binlog_format is set to MIXED and a given statement is replicated using the row-based format.

  Important

  Before enabling this variable, you must make certain that there are no dependencies between transactional and nontransactional tables; an example of such a dependency would be the statement INSERT INTO myisam_table SELECT * FROM innodb_table. Otherwise, such statements are likely to cause the slave to diverge from the master.

  In MySQL 5.6, this variable has no effect when the binary log format is ROW or MIXED. (Bug #51291)

• binlog_error_action

  Property	Value
  Command-Line Format	--binlog-error-action[=value]
  Introduced	5.6.22
  System Variable	binlog_error_action
  Scope	Global
  Dynamic	Yes
  Type	Enumeration
  Default Value	IGNORE_ERROR
  Valid Values	IGNORE_ERROR ABORT_SERVER

  Controls what happens when the server encounters an error such as not being able to write to, flush or synchronize the binary log, which can cause the master's binary log to become inconsistent and replication slaves to lose synchronization.

  In MySQL 5.6, this variable defaults to IGNORE_ERROR. If the server encounters such an error, it continues the ongoing transaction, logs the error then halts logging, and continues performing updates. To resume binary logging log_bin must be enabled again, which requires a server restart. This setting provides backward compatibility with older versions of MySQL.

  Setting this variable to ABORT_SERVER makes the server halt logging and shut down whenever it encounters such an error with the binary log. On restart, recovery proceeds as in the case of an unexpected server halt (see Section 17.3.2, “Handling an Unexpected Halt of a Replication Slave”). This is the recommended setting, particularly in complex replication environments.

  In previous releases this variable was named binlogging_impossible_mode.

• binlog_format

  Property	Value
  Command-Line Format	--binlog-format=format
  System Variable	binlog_format
  Scope	Global, Session
  Dynamic	Yes
  Type	Enumeration
  Default Value (>= 5.6.10-ndb-7.3.1)	MIXED
  Default Value	STATEMENT
  Valid Values	ROW STATEMENT MIXED

  This variable sets the binary logging format, and can be any one of STATEMENT, ROW, or MIXED. See Section 17.1.2, “Replication Formats”.

  binlog_format can be set at startup or at runtime, except that under some conditions, changing this variable at runtime is not possible or causes replication to fail, as described later.

  In MySQL 5.6, the default format is STATEMENT. Exception: In MySQL NDB Cluster 7.3 and later, the default is MIXED; statement-based replication is not supported for NDB Cluster.

  Setting the session value of this system variable is a restricted operation. The session user must have privileges sufficient to set restricted session variables. See Section 5.1.8.1, “System Variable Privileges”.

  The rules governing when changes to this variable take effect and how long the effect lasts are the same as for other MySQL server system variables. For more information, see Section 13.7.4.1, “SET Syntax for Variable Assignment”.

  When MIXED is specified, statement-based replication is used, except for cases where only row-based replication is guaranteed to lead to proper results. For example, this happens when statements contain user-defined functions (UDF) or the UUID() function.

  For details of how stored programs (stored procedures and functions, triggers, and events) are handled when each binary logging format is set, see Section 20.7, “Stored Program Binary Logging”.

  There are exceptions when you cannot switch the replication format at runtime:

  • From within a stored function or a trigger.

  • If the session is currently in row-based replication mode and has open temporary tables.

  • From within a transaction.

  Trying to switch the format in those cases results in an error.

  Changing the logging format on a replication master does not cause a replication slave to change its logging format to match. Switching the replication format while replication is ongoing can cause issues if a replication slave has binary logging enabled, and the change results in the slave using STATEMENT format logging while the master is using ROW or MIXED format logging. A replication slave is not able to convert binary log entries received in ROW logging format to STATEMENT format for use in its own binary log, so this situation can cause replication to fail. For more information, see Section 5.4.4.2, “Setting The Binary Log Format”.

  The binary log format affects the behavior of the following server options:

  • --replicate-do-db

  • --replicate-ignore-db

  • --binlog-do-db

  • --binlog-ignore-db

  These effects are discussed in detail in the descriptions of the individual options.

• binlogging_impossible_mode

  Property	Value
  Command-Line Format	--binlogging-impossible-mode[=value]
  Introduced	5.6.20
  Deprecated	5.6.22
  System Variable	binlogging_impossible_mode
  Scope	Global, Session
  Dynamic	Yes
  Type	Enumeration
  Default Value	IGNORE_ERROR
  Valid Values	IGNORE_ERROR ABORT_SERVER

  This option is deprecated and will be removed in a future MySQL release. Use the renamed binlog_error_action to control what happens when the server cannot write to the binary log.

• binlog_max_flush_queue_time

  Property	Value
  Command-Line Format	--binlog-max-flush-queue-time=#
  Introduced	5.6.6
  System Variable	binlog_max_flush_queue_time
  Scope	Global
  Dynamic	Yes
  Type	Integer
  Default Value	0
  Minimum Value	0
  Maximum Value	100000

  How long in microseconds to keep reading transactions from the flush queue before proceeding with the group commit (and syncing the log to disk, if sync_binlog is greater than 0). If the value is 0 (the default), there is no timeout and the server keeps reading new transactions until the queue is empty.

  Normally, binlog_max_flush_queue_time can remain set to 0. If the server processes a large number of connections (for example, 100 or more) and many short transactions with low-latency requirements, it may be useful to set the value larger than 0 to force more frequent flushes to disk.

• binlog_order_commits

  Property	Value
  Command-Line Format	--binlog-order-commits[={OFF|ON}]
  Introduced	5.6.6
  System Variable	binlog_order_commits
  Scope	Global
  Dynamic	Yes
  Type	Boolean
  Default Value	ON

  When this variable is enabled on a replication master (which is the default), transaction commit instructions issued to storage engines are serialized on a single thread, so that transactions are always committed in the same order as they are written to the binary log. Disabling this variable permits transaction commit instructions to be issued using multiple threads. Used in combination with binary log group commit, this prevents the commit rate of a single transaction being a bottleneck to throughput, and might therefore produce a performance improvement.

  Transactions are written to the binary log at the point when all the storage engines involved have confirmed that the transaction is prepared to commit. The binary log group commit logic then commits a group of transactions after their binary log write has taken place. When binlog_order_commits is disabled, because multiple threads are used for this process, transactions in a commit group might be committed in a different order from their order in the binary log. (Transactions from a single client always commit in chronological order.) In many cases this does not matter, as operations carried out in separate transactions should produce consistent results, and if that is not the case, a single transaction ought to be used instead.

• binlog_row_image

  Property	Value
  Command-Line Format	--binlog-row-image=image_type
  Introduced	5.6.2
  System Variable	binlog_row_image
  Scope	Global, Session
  Dynamic	Yes
  Type	Enumeration
  Default Value	full
  Valid Values	full (Log all columns) minimal (Log only changed columns, and columns needed to identify rows) noblob (Log all columns, except for unneeded BLOB and TEXT columns)

  For MySQL row-based replication, this variable determines how row images are written to the binary log.

  In MySQL row-based replication, each row change event contains two images, a “before” image whose columns are matched against when searching for the row to be updated, and an “after” image containing the changes. Normally, MySQL logs full rows (that is, all columns) for both the before and after images. However, it is not strictly necessary to include every column in both images, and we can often save disk, memory, and network usage by logging only those columns which are actually required.

  Note

  When deleting a row, only the before image is logged, since there are no changed values to propagate following the deletion. When inserting a row, only the after image is logged, since there is no existing row to be matched. Only when updating a row are both the before and after images required, and both written to the binary log.

  For the before image, it is necessary only that the minimum set of columns required to uniquely identify rows is logged. If the table containing the row has a primary key, then only the primary key column or columns are written to the binary log. Otherwise, if the table has a unique key all of whose columns are NOT NULL, then only the columns in the unique key need be logged. (If the table has neither a primary key nor a unique key without any NULL columns, then all columns must be used in the before image, and logged.) In the after image, it is necessary to log only the columns which have actually changed.

  In MySQL 5.6, you can cause the server to log full or minimal rows using the binlog_row_image system variable. This variable actually takes one of three possible values, as shown in the following list:

  • full: Log all columns in both the before image and the after image.

  • minimal: Log only those columns in the before image that are required to identify the row to be changed; log only those columns in the after image where a value was specified by the SQL statement, or generated by auto-increment.

  • noblob: Log all columns (same as full), except for BLOB and TEXT columns that are not required to identify rows, or that have not changed.

  Note

  This variable is not supported by NDB Cluster; setting it has no effect on the logging of NDB tables. (Bug #16316828)

  The default value is full.

  When using minimal or noblob, deletes and updates are guaranteed to work correctly for a given table if and only if the following conditions are true for both the source and destination tables:

  • All columns must be present and in the same order; each column must use the same data type as its counterpart in the other table.

  • The tables must have identical primary key definitions.

  (In other words, the tables must be identical with the possible exception of indexes that are not part of the tables' primary keys.)

  If these conditions are not met, it is possible that the primary key column values in the destination table may prove insufficient to provide a unique match for a delete or update. In this event, no warning or error is issued; the master and slave silently diverge, thus breaking consistency.

  Setting this variable has no effect when the binary logging format is STATEMENT. When binlog_format is MIXED, the setting for binlog_row_image is applied to changes that are logged using row-based format, but this setting no effect on changes logged as statements.

  Setting binlog_row_image on either the global or session level does not cause an implicit commit; this means that this variable can be changed while a transaction is in progress without affecting the transaction.

• binlog_rows_query_log_events

  Property	Value
  Command-Line Format	--binlog-rows-query-log-events[={OFF|ON}]
  Introduced	5.6.2
  System Variable	binlog_rows_query_log_events
  Scope	Global, Session
  Dynamic	Yes
  Type	Boolean
  Default Value	OFF

  This system variable affects row-based logging only. When enabled, it causes a MySQL 5.6.2 or higher server to write informational log events such as row query log events into its binary log. This information can be used for debugging and related purposes, such as obtaining the original query issued on the master when it cannot be reconstructed from the row updates. Must be disabled (the default) when generating logs for a MySQL 5.6.1 or earlier slave server or version of mysqlbinlog.

  These informational events are normally ignored by MySQL programs reading the binary log and so cause no issues when replicating or restoring from backup. To view them, increase the verbosity level by using mysqlbinlog's --verbose option twice, either as -vv or --verbose --verbose.

• binlog_stmt_cache_size

  Property	Value
  Command-Line Format	--binlog-stmt-cache-size=#
  Introduced	5.6.1
  System Variable	binlog_stmt_cache_size
  Scope	Global
  Dynamic	Yes
  Type	Integer
  Default Value	32768
  Minimum Value	4096
  Maximum Value (64-bit platforms)	18446744073709551615
  Maximum Value (32-bit platforms)	4294967295

  This variable determines the size of the cache for the binary log to hold nontransactional statements issued during a transaction. Separate binary log transaction and statement caches are allocated for each client if the server supports any transactional storage engines and if the server has the binary log enabled (--log-bin option). If you often use large nontransactional statements during transactions, you can increase this cache size to get better performance. The Binlog_stmt_cache_use and Binlog_stmt_cache_disk_use status variables can be useful for tuning the size of this variable. See Section 5.4.4, “The Binary Log”.

  The binlog_cache_size system variable sets the size for the transaction cache.

• expire_logs_days

  Property	Value
  Command-Line Format	--expire-logs-days=#
  System Variable	expire_logs_days
  Scope	Global
  Dynamic	Yes
  Type	Integer
  Default Value	0
  Minimum Value	0
  Maximum Value	99

  The number of days for automatic binary log file removal. The default is 0, which means “no automatic removal.” Possible removals happen at startup and when the binary log is flushed. Log flushing occurs as indicated in Section 5.4, “MySQL Server Logs”.

  To remove binary log files manually, use the PURGE BINARY LOGS statement. See Section 13.4.1.1, “PURGE BINARY LOGS Statement”.

• log_bin

  Property	Value
  System Variable	log_bin
  Scope	Global
  Dynamic	No
  Type	Boolean

  Whether the binary log is enabled. If the --log-bin option is used, then the value of this variable is ON; otherwise it is OFF. This variable reports only on the status of binary logging (enabled or disabled); it does not actually report the value to which --log-bin is set.

  See Section 5.4.4, “The Binary Log”.

• log_bin_basename

  Property	Value
  Introduced	5.6.2
  System Variable	log_bin_basename
  Scope	Global
  Dynamic	No
  Type	File name

  Holds the base name and path for the binary log files, which can be set with the --log-bin server option. In MySQL 5.6, the default base name is the name of the process ID file, with the suffix -bin. That name can be set with the --pid-file option, and it defaults to the name of the host machine. The default location for the binary log files is the data directory.

• log_bin_index

  Property	Value
  Command-Line Format	--log-bin-index=file_name
  System Variable (>= 5.6.4)	log_bin_index
  Scope (>= 5.6.4)	Global
  Dynamic (>= 5.6.4)	No
  Type	File name

  Holds the base name and path for the binary log index file, which can be set with the --log-bin-index server option.

• log_bin_trust_function_creators

  Property	Value
  Command-Line Format	--log-bin-trust-function-creators[={OFF|ON}]
  System Variable	log_bin_trust_function_creators
  Scope	Global
  Dynamic	Yes
  Type	Boolean
  Default Value	OFF

  This variable applies when binary logging is enabled. It controls whether stored function creators can be trusted not to create stored functions that will cause unsafe events to be written to the binary log. If set to 0 (the default), users are not permitted to create or alter stored functions unless they have the SUPER privilege in addition to the CREATE ROUTINE or ALTER ROUTINE privilege. A setting of 0 also enforces the restriction that a function must be declared with the DETERMINISTIC characteristic, or with the READS SQL DATA or NO SQL characteristic. If the variable is set to 1, MySQL does not enforce these restrictions on stored function creation. This variable also applies to trigger creation. See Section 20.7, “Stored Program Binary Logging”.

• log_bin_use_v1_row_events

  Property	Value
  Command-Line Format	--log-bin-use-v1-row-events[={OFF|ON}]
  Introduced	5.6.6
  System Variable	log_bin_use_v1_row_events
  Scope	Global
  Dynamic	No
  Type	Boolean
  Default Value	OFF

  Whether Version 2 binary logging is in use. If this variable is 0 (disabled, the default), Version 2 binary log events are in use. If this variable is 1 (enabled), the server writes the binary log using Version 1 logging events (the only version of binary log events used in previous releases), and thus produces a binary log that can be read by older slaves.

  Version 2 binary log row events are used by default beginning with MySQL 5.6.6; however, Version 2 events cannot be read by MySQL 5.6.5 and previous MySQL Server releases. Enabling log_bin_use_v1_row_events causes mysqld to write the binary log using Version 1 logging events.

  This variable is read-only at runtime. To switch between Version 1 and Version 2 binary event binary logging, it is necessary to set log_bin_use_v1_row_events at server startup.

  Other than when performing upgrades of NDB Cluster Replication, log_bin_use_v1_row_events is chiefly of interest when setting up replication conflict detection and resolution using NDB$EPOCH_TRANS() as the conflict detection function, which requires Version 2 binary log row events. Thus, this variable and --ndb-log-transaction-id are not compatible.

  Note

  MySQL NDB Cluster 7.3 and higher use Version 2 binary log row events by default. You should keep this mind when planning upgrades or downgrades, and for setups using NDB Cluster Replication.

  For more information, see Section 18.6.11, “NDB Cluster Replication Conflict Resolution”.

• log_slave_updates

  Property	Value
  Command-Line Format	--log-slave-updates[={OFF|ON}]
  System Variable	log_slave_updates
  Scope	Global
  Dynamic	No
  Type	Boolean
  Default Value	OFF

  Whether updates received by a slave server from a master server should be logged to the slave's own binary log.

  Normally, a slave does not log to its own binary log any updates that are received from a master server. Enabling this variable causes the slave to write the updates performed by its SQL thread to its own binary log. For this option to have any effect, the slave must also be started with the --log-bin option to enable binary logging. See Section 17.1.4, “Replication and Binary Logging Options and Variables”. A warning is issued if you enable log_slave_updates without also starting the server with the --log-bin option.

  log_slave_updates is enabled when you want to chain replication servers. For example, you might want to set up replication servers using this arrangement:

  A -> B -> C

  Here, A serves as the master for the slave B, and B serves as the master for the slave C. For this to work, B must be both a master and a slave. You must start both A and B with --log-bin to enable binary logging, and B with log_slave_updates enabled so that updates received from A are logged by B to its binary log.

• master_verify_checksum

  Property	Value
  Command-Line Format	--master-verify-checksum[={OFF|ON}]
  Introduced	5.6.2
  System Variable	master_verify_checksum
  Scope	Global
  Dynamic	Yes
  Type	Boolean
  Default Value	OFF

  Enabling this variable causes the master to verify events read from the binary log by examining checksums, and to stop with an error in the event of a mismatch. master_verify_checksum is disabled by default; in this case, the master uses the event length from the binary log to verify events, so that only complete events are read from the binary log.

• max_binlog_cache_size

  Property	Value
  Command-Line Format	--max-binlog-cache-size=#
  System Variable	max_binlog_cache_size
  Scope	Global
  Dynamic	Yes
  Type	Integer
  Default Value	18446744073709551615
  Minimum Value	4096
  Maximum Value	18446744073709551615

  If a transaction requires more than this many bytes of memory, the server generates a Multi-statement transaction required more than 'max_binlog_cache_size' bytes of storage error. The minimum value is 4096. The maximum possible value is 16EB (exabytes). The maximum recommended value is 4GB; this is due to the fact that MySQL currently cannot work with binary log positions greater than 4GB.

  Note

  Prior to MySQL 5.6.7, 64-bit Windows platforms truncated the stored value for this variable to 4G, even when it was set to a greater value (Bug #13961678).

  max_binlog_cache_size sets the size for the transaction cache only; the upper limit for the statement cache is governed by the max_binlog_stmt_cache_size system variable.

  In MySQL 5.6, the visibility to sessions of max_binlog_cache_size matches that of the binlog_cache_size system variable; in other words, changing its value effects only new sessions that are started after the value is changed.

• max_binlog_size

  Property	Value
  Command-Line Format	--max-binlog-size=#
  System Variable	max_binlog_size
  Scope	Global
  Dynamic	Yes
  Type	Integer
  Default Value	1073741824
  Minimum Value	4096
  Maximum Value	1073741824

  If a write to the binary log causes the current log file size to exceed the value of this variable, the server rotates the binary logs (closes the current file and opens the next one). The minimum value is 4096 bytes. The maximum and default value is 1GB.

  A transaction is written in one chunk to the binary log, so it is never split between several binary logs. Therefore, if you have big transactions, you might see binary log files larger than max_binlog_size.

  If max_relay_log_size is 0, the value of max_binlog_size applies to relay logs as well.

• max_binlog_stmt_cache_size

  Property	Value
  Command-Line Format	--max-binlog-stmt-cache-size=#
  Introduced	5.6.1
  System Variable	max_binlog_stmt_cache_size
  Scope	Global
  Dynamic	Yes
  Type	Integer
  Default Value	18446744073709547520
  Minimum Value	4096
  Maximum Value	18446744073709547520

  If nontransactional statements within a transaction require more than this many bytes of memory, the server generates an error. The minimum value is 4096. The maximum and default values are 4GB on 32-bit platforms and 16EB (exabytes) on 64-bit platforms.

  Note

  Prior to MySQL 5.6.7, 64-bit Windows platforms truncated the stored value for this variable to 4G, even when it was set to a greater value (Bug #13961678).

  max_binlog_stmt_cache_size sets the size for the statement cache only; the upper limit for the transaction cache is governed exclusively by the max_binlog_cache_size system variable.

• sql_log_bin

  Property	Value
  System Variable	sql_log_bin
  Scope	Session
  Dynamic	Yes
  Type	Boolean
  Default Value	ON

  This variable controls whether logging to the binary log is enabled for the current session (assuming that the binary log itself is enabled). The default value is ON. To disable or enable binary logging for the current session, set the session sql_log_bin variable to OFF or ON.

  Set this variable to OFF for a session to temporarily disable binary logging while making changes to the master you do not want replicated to the slave.

  Setting the session value of this system variable is a restricted operation. The session user must have privileges sufficient to set restricted session variables. See Section 5.1.8.1, “System Variable Privileges”.

  It is not possible to set the session value of sql_log_bin within a transaction or subquery.

  Setting this variable to OFF prevents GTIDs from being assigned to transactions in the binary log. If you are using GTIDs for replication, this means that, even when binary logging is later enabled once again, the GTIDs written into the log from this point do not account for any transactions that occurred in the meantime—in effect, those transactions are lost.

  As of MySQL 5.6.22, the global sql_log_bin variable is read only and cannot be modified. The global scope is deprecated and will be removed in a future MySQL release. Prior to 5.6.22, sql_log_bin can be set as a global or session variable. Setting sql_log_bin globally is only detected when a new session is started. Any sessions previously running are not impacted when setting sql_log_bin globally.

  Warning

  Incorrect use of sql_log_bin with a global scope means any changes made in an already running session are still being recorded to the binary log and therefore replicated. Exercise extreme caution using sql_log_bin with a global scope as the above situation could cause unexpected results including replication failure.

• sync_binlog

  Property	Value
  Command-Line Format	--sync-binlog=#
  System Variable	sync_binlog
  Scope	Global
  Dynamic	Yes
  Type	Integer
  Default Value	0
  Minimum Value	0
  Maximum Value	4294967295

  Controls how often the MySQL server synchronizes the binary log to disk.

  • sync_binlog=0: Disables synchronization of the binary log to disk by the MySQL server. Instead, the MySQL server relies on the operating system to flush the binary log to disk from time to time as it does for any other file. This setting provides the best performance, but in the event of a power failure or operating system crash, it is possible that the server has committed transactions that have not been synchronized to the binary log.

  • sync_binlog=1: Enables synchronization of the binary log to disk before transactions are committed. This is the safest setting but can have a negative impact on performance due to the increased number of disk writes. In the event of a power failure or operating system crash, transactions that are missing from the binary log are only in a prepared state. This permits the automatic recovery routine to roll back the transactions, which guarantees that no transaction is lost from the binary log.

  • sync_binlog=N, where N is a value other than 0 or 1: The binary log is synchronized to disk after N binary log commit groups have been collected. In the event of a power failure or operating system crash, it is possible that the server has committed transactions that have not been flushed to the binary log. This setting can have a negative impact on performance due to the increased number of disk writes. A higher value improves performance, but with an increased risk of data loss.

  For the greatest possible durability and consistency in a replication setup that uses InnoDB with transactions, use these settings:

  • sync_binlog=1.

  • innodb_flush_log_at_trx_commit=1.

  Caution

  Many operating systems and some disk hardware fool the flush-to-disk operation. They may tell mysqld that the flush has taken place, even though it has not. In this case, the durability of transactions is not guaranteed even with the recommended settings, and in the worst case, a power outage can corrupt InnoDB data. Using a battery-backed disk cache in the SCSI disk controller or in the disk itself speeds up file flushes, and makes the operation safer. You can also try to disable the caching of disk writes in hardware caches.