17.1.6.4 Binary Logging Options and Variables

--binlog-row-event-max-size=N

When row-based binary logging is used, this setting is a soft limit on the maximum size of a row-based binary log event, in bytes. Where possible, rows stored in the binary log are grouped into events with a size not exceeding the value of this setting. If an event cannot be split, the maximum size can be exceeded. The value must be (or else gets rounded down to) a multiple of 256. The default is 8192 bytes.

--log-bin[=base_name]

Specifies the base name to use for binary log files. 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. The --log-bin option value 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.

If you do not supply the --log-bin option, MySQL uses binlog as the default base name for the binary log files. For compatibility with earlier releases, if you supply the --log-bin option with no string or with an empty string, the base name defaults to host_name-bin, using the name of the host machine.

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. The binary log file base name and any specified path are available as the log_bin_basename system variable.

In earlier MySQL versions, binary logging was disabled by default, and was enabled if you specified the --log-bin option. From MySQL 8.0, binary logging is enabled by default, whether or not you specify the --log-bin option. The exception is if you use mysqld to initialize the data directory manually by invoking it with the --initialize or --initialize-insecure option, when binary logging is disabled by default. It is possible to enable binary logging in this case by specifying the --log-bin option. When binary logging is enabled, the log_bin system variable, which shows the status of binary logging on the server, is set to ON.

To disable binary logging, you can specify the --skip-log-bin or --disable-log-bin option at startup. If either of these options is specified and --log-bin is also specified, the option specified later takes precedence. When binary logging is disabled, the log_bin system variable is set to OFF.

When GTIDs are in use on the server, if you disable binary logging when restarting the server after an abnormal shutdown, some GTIDs are likely to be lost, causing replication to fail. In a normal shutdown, the set of GTIDs from the current binary log file is saved in the mysql.gtid_executed table. Following an abnormal shutdown where this did not happen, during recovery the GTIDs are added to the table from the binary log file, provided that binary logging is still enabled. If binary logging is disabled for the server restart, the server cannot access the binary log file to recover the GTIDs, so replication cannot be started. Binary logging can be disabled safely after a normal shutdown.

The --log-slave-updates and --slave-preserve-commit-order options require binary logging. If you disable binary logging, either omit these options, or specify --skip-log-slave-updates and --skip-slave-preserve-commit-order. MySQL disables these options by default when --skip-log-bin or --disable-log-bin is specified. If you specify --log-slave-updates or --slave-preserve-commit-order together with --skip-log-bin or --disable-log-bin, a warning or error message is issued.

In MySQL 5.7, a server ID had to be specified when binary logging was enabled, or the server would not start. In MySQL 8.0, the server_id system variable is set to 1 by default. The server can now be started with this default server ID when binary logging is enabled, but an informational message is issued if you do not specify a server ID explicitly using the --server-id option. For servers that are used in a replication topology, you must specify a unique nonzero server ID for each server.

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

--log-bin-index[=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 specify --log-bin option with no string or an empty string, 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”.

--log-bin-trust-function-creators[={0|1}]

This option sets the corresponding log_bin_trust_function_creators system variable. If no argument is given, the option sets the variable to 1. log_bin_trust_function_creators affects how MySQL enforces restrictions on stored function and trigger creation. See Section 24.7, “Stored Program Binary Logging”.

--log-bin-use-v1-row-events[={OFF|ON}]

This option is deprecated. Setting the option to ON enabled row-based replication with slaves running MySQL Server 5.5 and earlier by writing the binary log using Version 1 binary log row events, instead of Version 2 binary log row events which are the default from MySQL 5.6.

--binlog-do-db=db_name

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.

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:

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:

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:

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:

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:

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:

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

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.

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:

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.

--binlog-checksum={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, and CRC32 is the default. You cannot change the setting for this option within a transaction.

--master-verify-checksum={0|1}

Enabling this option causes the master to verify events from the binary log using checksums, and to stop with an error in the event of a mismatch. Disabled by default.

--max-binlog-dump-events=N

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

--sporadic-binlog-dump-fail

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

binlog_cache_size

The size of the memory buffer to hold changes to the binary log during a transaction. When binary logging is enabled on the server (with the log_bin system variable set to ON), a binary log cache is allocated for each client if the server supports any transactional storage engines. If the data for the transaction exceeds the space in the memory buffer, the excess data is stored in a temporary file. When binary log encryption is active on the server, the memory buffer is not encrypted, but (from MySQL 8.0.17) any temporary file used to hold the binary log cache is encrypted. After each transaction is committed, the binary log cache is reset by clearing the memory buffer and truncating the temporary file if used.

If you often use large transactions, you can increase this cache size to get better performance by reducing or eliminating the need to write to temporary files. 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

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. You cannot change the value of binlog_checksum within a transaction.

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.

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

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.

As of MySQL 8.0.14, 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 5.1.9.1, “System Variable Privileges”.

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.

This variable has no effect when the binary log format is ROW or MIXED.

binlog_encryption

Enables encryption for binary log files and relay log files on this server. OFF is the default. ON sets encryption on for binary log files and relay log files. Binary logging does not need to be enabled on the server to enable encryption, so you can encrypt the relay log files on a slave that has no binary log. To use encryption, a keyring plugin must be installed and configured to supply MySQL Server's keyring service. For instructions to do this, see Section 6.4.4, “The MySQL Keyring”. Any supported keyring plugin can be used to store binary log encryption keys.

When you first start the server with binary log encryption enabled, a new binary log encryption key is generated before the binary log and relay logs are initialized. This key is used to encrypt a file password for each binary log file (if the server has binary logging enabled) and relay log file (if the server has replication channels), and further keys generated from the file passwords are used to encrypt the data in the files. Relay log files are encrypted for all channels, including Group Replication applier channels and new channels that are created after encryption is activated. The binary log index file and relay log index file are never encrypted.

If you activate encryption while the server is running, a new binary log encryption key is generated at that time. The exception is if encryption was active previously on the server and was then disabled, in which case the binary log encryption key that was in use before is used again. The binary log file and relay log files are rotated immediately, and file passwords for the new files and all subsequent binary log files and relay log files are encrypted using this binary log encryption key. Existing binary log files and relay log files still present on the server are not automatically encrypted, but you can purge them if they are no longer needed.

If you deactivate encryption by changing the binlog_encryption system variable to OFF, the binary log file and relay log files are rotated immediately and all subsequent logging is unencrypted. Previously encrypted files are not automatically decrypted, but the server is still able to read them. SUPER privileges or the BINLOG_ENCRYPTION_ADMIN privilege are required to activate or deactivate encryption while the server is running. Group Replication applier channels are not included in the relay log rotation request, so unencrypted logging for these channels does not start until their logs are rotated in normal use.

For more information on binary log file and relay log file encryption, see Section 17.3.10, “Encrypting Binary Log Files and Relay Log Files”.

binlog_error_action

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.

This variable defaults to ABORT_SERVER, which 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”).

When binlog_error_action is set 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.

binlog_expire_logs_seconds

Sets the binary log expiration period in seconds. After their expiration period ends, binary log files can be automatically removed. Possible removals happen at startup and when the binary log is flushed. Log flushing occurs as indicated in Section 5.4, “MySQL Server Logs”.

The default binary log expiration period is 2592000 seconds, which equals 30 days (30*24*60*60 seconds). The default applies if neither binlog_expire_logs_seconds nor the deprecated system variable expire_logs_days has a value set at startup. If a non-zero value for one of the variables binlog_expire_logs_seconds or expire_logs_days is set at startup, this value is used as the binary log expiration period. If a non-zero value for both of those variables is set at startup, the value for binlog_expire_logs_seconds is used as the binary log expiration period, and the value for expire_logs_days is ignored with a warning message.

To disable automatic purging of the binary log, specify a value of 0 explicitly for binlog_expire_logs_seconds, and do not specify a value for expire_logs_days. For compatibility with earlier releases, automatic purging is also disabled if you specify a value of 0 explicitly for expire_logs_days and do not specify a value for binlog_expire_logs_seconds. In that case, the default for binlog_expire_logs_seconds is not applied.

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

binlog_format

This variable sets the binary logging format, and can be any one of STATEMENT, ROW, or MIXED. See Section 17.2.1, “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.

The default is ROW. Exception: In NDB Cluster, 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 5.1.9.1, “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 13.7.5.1, “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 24.7, “Stored Program Binary Logging”.

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

Trying to switch the replication format in any of these cases (or attempting to set the current replication format) results in an error. You can, however, use PERSIST_ONLY (SET @@PERSIST_ONLY.binlog_format) to change the replication format at any time, because this action does not modify the runtime global system variable value, and takes effect only after a server restart.

Switching the replication format at runtime is not recommended when any temporary tables exist, because temporary tables are logged only when using statement-based replication, whereas with row-based replication and mixed replication, they are not logged.

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:

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

binlog_group_commit_sync_delay

Controls how many microseconds the binary log commit waits before synchronizing the binary log file to disk. By default binlog_group_commit_sync_delay is set to 0, meaning that there is no delay. Setting binlog_group_commit_sync_delay to a microsecond delay enables more transactions to be synchronized together to disk at once, reducing the overall time to commit a group of transactions because the larger groups require fewer time units per group.

When sync_binlog=0 or sync_binlog=1 is set, the delay specified by binlog_group_commit_sync_delay is applied for every binary log commit group before synchronization (or in the case of sync_binlog=0, before proceeding). When sync_binlog is set to a value n greater than 1, the delay is applied after every n binary log commit groups.

Setting binlog_group_commit_sync_delay can increase the number of parallel committing transactions on any server that has (or might have after a failover) a replication slave, and therefore can increase parallel execution on the replication slaves. To benefit from this effect, the slave servers must have slave_parallel_type=LOGICAL_CLOCK set, and the effect is more significant when binlog_transaction_dependency_tracking=COMMIT_ORDER is also set. It is important to take into account both the master's throughput and the slaves' throughput when you are tuning the setting for binlog_group_commit_sync_delay.

Setting binlog_group_commit_sync_delay can also reduce the number of fsync() calls to the binary log on any server (master or slave) that has a binary log.

Note that setting binlog_group_commit_sync_delay increases the latency of transactions on the server, which might affect client applications. Also, on highly concurrent workloads, it is possible for the delay to increase contention and therefore reduce throughput. Typically, the benefits of setting a delay outweigh the drawbacks, but tuning should always be carried out to determine the optimal setting.

binlog_group_commit_sync_no_delay_count

The maximum number of transactions to wait for before aborting the current delay as specified by binlog_group_commit_sync_delay. If binlog_group_commit_sync_delay is set to 0, then this option has no effect.

binlog_max_flush_queue_time

binlog_max_flush_queue_time is deprecated, and is marked for eventual removal in a future MySQL release. Formerly, this system variable controlled the time in microseconds to continue reading transactions from the flush queue before proceeding with group commit. It no longer has any effect.

binlog_order_commits

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.

If you want to ensure that the transaction history on the master and on a multithreaded replication slave remains identical, set slave_preserve_commit_order=1 on the replication slave.

binlog_rotate_encryption_master_key_at_startup

Specifies whether or not the binary log master key is rotated at server startup. The binary log master key is the binary log encryption key that is used to encrypt file passwords for the binary log files and relay log files on the server. When a server is started for the first time with binary log encryption enabled (binlog_encryption=ON), a new binary log encryption key is generated and used as the binary log master key. If the binlog_rotate_encryption_master_key_at_startup system variable is also set to ON, whenever the server is restarted, a further binary log encryption key is generated and used as the binary log master key for all subsequent binary log files and relay log files. If the binlog_rotate_encryption_master_key_at_startup system variable is set to OFF, which is the default, the existing binary log master key is used again after the server restarts. For more information on binary log encryption keys and the binary log master key, see Section 17.3.10, “Encrypting Binary Log Files and Relay Log Files”.

binlog_row_event_max_size

When row-based binary logging is used, this setting is a soft limit on the maximum size of a row-based binary log event, in bytes. Where possible, rows stored in the binary log are grouped into events with a size not exceeding the value of this setting. If an event cannot be split, the maximum size can be exceeded. The value must be (or else gets rounded down to) a multiple of 256. The default is 8192 bytes.

This global system variable is read-only and can be set only at server startup. Its value can therefore only be modified by using the PERSIST_ONLY keyword or the @@persist_only qualifier with the SET statement.

binlog_row_image

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

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 5.1.9.1, “System Variable Privileges”.

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.

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.

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:

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:

(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_row_metadata

Configures the amount of table metadata added to the binary log when using row-based logging. When set to MINIMAL, the default, only metadata related to SIGNED flags, column character set and geometry types are logged. When set to FULL complete metadata for tables is logged, such as column name, ENUM or SET string values, PRIMARY KEY information, and so on.

The extended metadata serves the following purposes:

binlog_row_value_options

When set to PARTIAL_JSON, this enables use of a space-efficient binary log format for updates that modify only a small portion of a JSON document, which causes row-based replication to write only the modified parts of the JSON document to the after-image for the update in the binary log (rather than writing the full document). This works for an UPDATE statement which modifies a JSON column using any sequence of JSON_SET(), JSON_REPLACE(), and JSON_REMOVE(). If the modification requires more space than the full document, or if the server is unable to generate a partial update, the full document is used instead.

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 5.1.9.1, “System Variable Privileges”.

PARTIAL_JSON is the only supported value; to unset binlog_row_value_options, set its value to the empty string.

binlog_row_value_options=PARTIAL_JSON takes effect only when binary logging is enabled and binlog_format is set to ROW or MIXED. Statement-based replication always logs only the modified parts of the JSON document, regardless of any value set for binlog_row_value_options. To maximize the amount of space saved, use binlog_row_image=NOBLOB or binlog_row_image=MINIMAL together with this option. binlog_row_image=FULL saves less space than either of these, since the full JSON document is stored in the before-image, and the partial update is stored only in the after-image.

mysqlbinlog output includes partial JSON updates in the form of events encoded as base-64 strings using BINLOG statements. If the --verbose option is specified, mysqlbinlog displays the partial JSON updates as readable JSON using pseudo-SQL statements.

MySQL Replication generates an error if a modification cannot be applied to the JSON document on the slave. This includes a failure to find the path. Be aware that, even with this and other safety checks, if a JSON document on a slave has diverged from that on the master and a partial update is applied, it remains theoretically possible to produce a valid but unexpected JSON document on the slave.

binlog_rows_query_log_events

This system variable affects row-based logging only. When enabled, it causes the 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.

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 5.1.9.1, “System Variable Privileges”.

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

The size of the memory buffer for the binary log to hold nontransactional statements issued during a transaction. When binary logging is enabled on the server (with the log_bin system variable set to ON), separate binary log transaction and statement caches are allocated for each client if the server supports any transactional storage engines. If the data for the nontransactional statements used in the transaction exceeds the space in the memory buffer, the excess data is stored in a temporary file. When binary log encryption is active on the server, the memory buffer is not encrypted, but (from MySQL 8.0.17) any temporary file used to hold the binary log cache is encrypted. After each transaction is committed, the binary log statement cache is reset by clearing the memory buffer and truncating the temporary file if used.

If you often use large nontransactional statements during transactions, you can increase this cache size to get better performance by reducing or eliminating the need to write to temporary files. 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.

binlog_transaction_dependency_tracking

The source of dependency information that the master uses to determine which transactions can be executed in parallel by the slave's multithreaded applier. This variable can take one of the three values described in the following list:

WRITESET and WRITESET_SESSION modes do not deliver any transaction dependencies that are newer than those that would have been returned in COMMIT_ORDER mode.

The value of this variable cannot be set to anything other than COMMIT_ORDER if transaction_write_set_extraction is OFF. You should also note that the value of transaction_write_set_extraction cannot be changed if the current value of binlog_transaction_dependency_tracking is WRITESET or WRITESET_SESSION.

The number of row hashes to be kept and checked for the latest transaction to have changed a given row is determined by the value of binlog_transaction_dependency_history_size.

binlog_transaction_dependency_history_size

Sets an upper limit on the number of row hashes which are kept in memory and used for looking up the transaction that last modified a given row. Once this number of hashes has been reached, the history is purged.

expire_logs_days

Specifies the number of days before automatic removal of binary log files. expire_logs_days is deprecated, and will be removed in a future release. Instead, use binlog_expire_logs_seconds, which sets the binary log expiration period in seconds. If you do not set a value for either system variable, the default expiration period is 30 days. Possible removals happen at startup and when the binary log is flushed. Log flushing occurs as indicated in Section 5.4, “MySQL Server Logs”.

Any non-zero value that you specify for expire_logs_days is ignored if binlog_expire_logs_seconds is also specified, and the value of binlog_expire_logs_seconds is used instead as the binary log expiration period. A warning message is issued in this situation. A non-zero value for expire_logs_days is only applied as the binary log expiration period if binlog_expire_logs_seconds is not specified or is specified as 0.

To disable automatic purging of the binary log, specify a value of 0 explicitly for binlog_expire_logs_seconds, and do not specify a value for expire_logs_days. For compatibility with earlier releases, automatic purging is also disabled if you specify a value of 0 explicitly for expire_logs_days and do not specify a value for binlog_expire_logs_seconds. In that case, the default for binlog_expire_logs_seconds is not applied.

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

log_bin

Shows the status of binary logging on the server, either enabled (ON) or disabled (OFF). With binary logging enabled, the server logs all statements that change data to the binary log, which is used for backup and replication. ON means that the binary log is available, OFF means that it is not in use. The --log-bin option can be used to specify a base name and location for the binary log.

In earlier MySQL versions, binary logging was disabled by default, and was enabled if you specified the --log-bin option. From MySQL 8.0, binary logging is enabled by default, with the log_bin system variable set to ON, whether or not you specify the --log-bin option. The exception is if you use mysqld to initialize the data directory manually by invoking it with the --initialize or --initialize-insecure option, when binary logging is disabled by default. It is possible to enable binary logging in this case by specifying the --log-bin option.

If the --skip-log-bin or --disable-log-bin option is specified at startup, binary logging is disabled, with the log_bin system variable set to OFF. If either of these options is specified and --log-bin is also specified, the option specified later takes precedence.

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

log_bin_basename

Holds the base name and path for the binary log files, which can be set with the --log-bin server option. In MySQL 8.0, if the --log-bin option is not supplied, the default base name is binlog. For compatibility with MySQL 5.7, if the --log-bin option is supplied with no string or with an empty string, the default base name is host_name-bin, using the name of the host machine. The default location is the data directory.

log_bin_index

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

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 24.7, “Stored Program Binary Logging”.

log_bin_use_v1_row_events

This read-only system variable is deprecated. Setting the system variable to ON (using the --log-bin-use-v1-row-events option) enabled row-based replication with slaves running MySQL Server 5.5 and earlier by writing the binary log using Version 1 binary log row events, instead of Version 2 binary log row events which are the default from MySQL 5.6.

log_builtin_as_identified_by_password

This system variable was removed in MySQL 8.0.11.

log_slave_updates

Whether updates received by a slave server from a master server should be logged to the slave's own binary log. Binary logging must be enabled on the slave for this variable to have any effect. See Section 17.1.6, “Replication and Binary Logging Options and Variables”.

This system variable is set on by default, and is read-only. If you need to prevent the slave server from logging updates, specify --skip-log-slave-updates when you start the slave, or specify log_slave_updates=OFF in the configuration file for the slave.

log_statements_unsafe_for_binlog

If error 1592 is encountered, controls whether the generated warnings are added to the error log or not.

master_verify_checksum

Enabling this variable causes the master to examine checksums when reading from the binary log. 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

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 16EiB (exbibytes). The maximum recommended value is 4GB; this is due to the fact that MySQL currently cannot work with binary log positions greater than 4GB.

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.

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

max_binlog_size

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. Encrypted binary log files have an additional 512-byte header, which is included in max_binlog_size.

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.

With GTIDs in use on the server, when max_binlog_size is reached, if the system table mysql.gtid_executed cannot be accessed to write the GTIDs from the current binary log file, the binary log cannot be rotated. In this situation, the server responds according to its binlog_error_action setting. If IGNORE_ERROR is set, an error is logged on the server and binary logging is halted, or if ABORT_SERVER is set, the server shuts down.

max_binlog_stmt_cache_size

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.

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.

original_commit_timestamp

For internal use by replication. When re-executing a transaction on a slave, this is set to the time when the transaction was committed on the original master, measured in microseconds since the epoch. This allows the original commit timestamp to be propagated throughout a replication topology.

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 5.1.9.1, “System Variable Privileges”.

sql_log_bin

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 5.1.9.1, “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 again, the GTIDs written into the log from this point do not account for any transactions that occurred in the meantime, so in effect those transactions are lost.

sync_binlog

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

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

transaction_write_set_extraction

Defines the algorithm used to hash the writes extracted during a transaction. If you are using Group Replication, this variable must be set to XXHASH64 because the process of extracting the writes from a transaction is required for conflict detection on all group members. See Section 18.9.1, “Group Replication Requirements”.

As of MySQL 8.0.14, 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 5.1.9.1, “System Variable Privileges”.