19.1.6.4 Binary Logging Options and Variables (original) (raw)

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 usingSET. Server options used to control binary logging are listed earlier in this section.

• binlog_cache_size

  Command-Line Format	--binlog-cache-size=#
  System Variable	binlog_cache_size
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value	32768
  Minimum Value	4096
  Maximum Value (64-bit platforms)	18446744073709547520
  Maximum Value (32-bit platforms)	4294963200
  Unit	bytes
  Block Size	4096
  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 thelog_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 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. TheBinlog_cache_use andBinlog_cache_disk_use status variables can be useful for tuning the size of this variable. See Section 7.4.4, “The Binary Log”.
  binlog_cache_size sets the size for the transaction cache only; the size of the statement cache is governed by thebinlog_stmt_cache_size system variable.

• binlog_checksum

  Command-Line Format	--binlog-checksum=type
  System Variable	binlog_checksum
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	String
  Default Value	CRC32
  Valid Values	NONECRC32
  When enabled, this variable causes the source to write a checksum for each event in the binary log.binlog_checksum supports the valuesNONE (which disables checksums) andCRC32. The default isCRC32. Whenbinlog_checksum is disabled (valueNONE), 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.
  Setting this variable on the source to a value unrecognized by the replica causes the replica to set its ownbinlog_checksum value toNONE, and to stop replication with an error. If backward compatibility with older replicas is a concern, you may want to set the value explicitly toNONE.
  Group Replication in MySQL 8.4 supports checksums, so group members may use the default setting.
  Changing the value of binlog_checksum causes the binary log to be rotated, because checksums must be written for an entire binary log file, and never for only part of one. You cannot change the value ofbinlog_checksum within a transaction.
  When binary log transaction compression is enabled using thebinlog_transaction_compression system variable, checksums are not written for individual events in a compressed transaction payload. Instead a checksum is written for the GTID event, and a checksum for the compressed Transaction_payload_event.

• binlog_direct_non_transactional_updates
  Due to concurrency issues, a replica 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.
  Thebinlog_direct_non_transactional_updates variable offers one possible workaround to this issue. By default, this variable is disabled. Enablingbinlog_direct_non_transactional_updates causes updates to nontransactional tables to be written directly to the binary log, rather than to the transaction cache.
  Setting the session value of this system variable is a restricted operation. The session user must have privileges sufficient to set restricted session variables. SeeSection 7.1.9.1, “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 ofbinlog_format isSTATEMENT, or whenbinlog_format isMIXED and a given statement is being replicated using the statement-based format. This variable has no effect when the binary log format isROW, or whenbinlog_format is set toMIXED 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 replica to diverge from the source.
  This variable has no effect when the binary log format isROW or MIXED.
• binlog_encryption

  Command-Line Format	--binlog-encryption[={OFF|ON}]
  System Variable	binlog_encryption
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Boolean
  Default Value	OFF
  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 replica 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 8.4.4, “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 thebinlog_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. The BINLOG_ENCRYPTION_ADMIN privilege (or the deprecatedSUPER privilege) is 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, seeSection 19.3.2, “Encrypting Binary Log Files and Relay Log Files”.

• binlog_error_action

  Command-Line Format	--binlog-error-action[=value]
  System Variable	binlog_error_action
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Enumeration
  Default Value	ABORT_SERVER
  Valid Values	IGNORE_ERRORABORT_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 source's binary log to become inconsistent and replicas 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 (seeSection 19.4.2, “Handling an Unexpected Halt of a Replica”).
  When binlog_error_action is set toIGNORE_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 logginglog_bin must be enabled again, which requires a server restart. This setting provides backward compatibility with older versions of MySQL.

• binlog_expire_logs_seconds

  Command-Line Format	--binlog-expire-logs-seconds=#
  System Variable	binlog_expire_logs_seconds
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value	2592000
  Minimum Value	0
  Maximum Value	4294967295
  Unit	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 7.4, “MySQL Server Logs”.
  The default binary log expiration period is 2592000 seconds, which equals 30 days (30*24*60*60 seconds).
  Automatic purging of the binary log can be disabled by setting thebinlog_expire_logs_auto_purge system variable to OFF. This takes precedence over any setting forbinlog_expire_logs_seconds.
  To remove binary log files manually, use thePURGE BINARY LOGS statement. See Section 15.4.1.1, “PURGE BINARY LOGS Statement”.

• binlog_expire_logs_auto_purge

  Command-Line Format	--binlog-expire-logs-auto-purge={ON|OFF}
  System Variable	binlog_expire_logs_auto_purge
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Boolean
  Default Value	ON
  Enables or disables automatic purging of binary log files. Setting this variable to ON (the default) enables automatic purging; setting it toOFF disables automatic purging. The interval to wait before purging is controlled bybinlog_expire_logs_seconds.
  Note
  Even if binlog_expire_logs_auto_purge is ON, settingbinlog_expire_logs_seconds to0 stops automatic purging from taking place.
  This variable has no effect on PURGE BINARY LOGS.

• binlog_format

  Command-Line Format	--binlog-format=format
  Deprecated	Yes
  System Variable	binlog_format
  Scope	Global, Session
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Enumeration
  Default Value	ROW
  Valid Values	MIXEDSTATEMENTROW
  This system variable sets the binary logging format, and can be any one of STATEMENT,ROW, or MIXED. (SeeSection 19.2.1, “Replication Formats”.) The setting takes effect when binary logging is enabled on the server, which is the case when thelog_bin system variable is set to ON. In MySQL 8.4, binary logging is enabled by default, and by default uses the row-based format.
  Note
  binlog_format is deprecated, and subject to removal in a future version of MySQL. This implies that support for logging formats other than row-based is also subject to removal in a future release. Thus, only row-based logging should be employed for any new MySQL Replication setups.
  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. SeeSection 7.1.9.1, “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 15.7.6.1, “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 loadable functions 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, seeSection 27.7, “Stored Program Binary Logging”.
  There are exceptions when you cannot switch the replication format at runtime:

  • The replication format cannot be changed from within a stored function or a trigger.
  • If a session has open temporary tables, the replication format cannot be changed for the session (SET @@SESSION.binlog_format).
  • If any replication channel has open temporary tables, the replication format cannot be changed globally (SET @@GLOBAL.binlog_format orSET @@PERSIST.binlog_format).
  • If any replication channel applier thread is currently running, the replication format cannot be changed globally (SET @@GLOBAL.binlog_format or SET @@PERSIST.binlog_format).
    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, usePERSIST_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 source server does not cause a replica to change its logging format to match. Switching the replication format while replication is ongoing can cause issues if a replica has binary logging enabled, and the change results in the replica usingSTATEMENT format logging while the source is using ROW or MIXED format logging. A replica is not able to convert binary log entries received in ROW logging format toSTATEMENT format for use in its own binary log, so this situation can cause replication to fail. For more information, seeSection 7.4.4.2, “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.
• binlog_group_commit_sync_delay

  Command-Line Format	--binlog-group-commit-sync-delay=#
  System Variable	binlog_group_commit_sync_delay
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value	0
  Minimum Value	0
  Maximum Value	1000000
  Unit	microseconds
  Controls how many microseconds the binary log commit waits before synchronizing the binary log file to disk. By defaultbinlog_group_commit_sync_delay is set to 0, meaning that there is no delay. Settingbinlog_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 orsync_binlog=1 is set, the delay specified bybinlog_group_commit_sync_delay is applied for every binary log commit group before synchronization (or in the case ofsync_binlog=0, before proceeding). Whensync_binlog is set to a value n greater than 1, the delay is applied after every n binary log commit groups.
  Settingbinlog_group_commit_sync_delay can increase the number of parallel committing transactions on any server that has (or might have after a failover) a replica, and therefore can increase parallel execution on the replicas. To benefit from this effect, the replica servers must havereplica_parallel_type=LOGICAL_CLOCK set. It is important to take into account both source and replica throughput when you are settingbinlog_group_commit_sync_delay.
  Settingbinlog_group_commit_sync_delay can also reduce the number of fsync() calls to the binary log on any server (source or replica) that has a binary log.
  Note that settingbinlog_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

  Command-Line Format	--binlog-group-commit-sync-no-delay-count=#
  System Variable	binlog_group_commit_sync_no_delay_count
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value	0
  Minimum Value	0
  Maximum Value	100000
  The maximum number of transactions to wait for before aborting the current delay as specified bybinlog_group_commit_sync_delay. Ifbinlog_group_commit_sync_delay is set to 0, then this option has no effect.

• binlog_max_flush_queue_time

  Command-Line Format	--binlog-max-flush-queue-time=#
  Deprecated	Yes
  System Variable	binlog_max_flush_queue_time
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value	0
  Minimum Value	0
  Maximum Value	100000
  Unit	microseconds
  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

  Command-Line Format	--binlog-order-commits[={OFF|ON}]
  System Variable	binlog_order_commits
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Boolean
  Default Value	ON
  When this variable is enabled on a replication source server (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. Whenbinlog_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 source and on a multithreaded replica remains identical, setreplica_preserve_commit_order=1 on the replica.

• 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 thebinlog_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 thebinlog_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 19.3.2, “Encrypting Binary Log Files and Relay Log Files”.
• binlog_row_event_max_size

  Command-Line Format	--binlog-row-event-max-size=#
  System Variable	binlog_row_event_max_size
  Scope	Global
  Dynamic	No
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value	8192
  Minimum Value	256
  Maximum Value (64-bit platforms)	18446744073709551615
  Maximum Value (32-bit platforms)	4294967295
  Unit	bytes
  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 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 theSET statement.

• binlog_row_image

  Command-Line Format	--binlog-row-image=image_type
  System Variable	binlog_row_image
  Scope	Global, Session
  Dynamic	Yes
  SET_VAR Hint Applies	No
  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.
  Setting the session value of this system variable is a restricted operation. The session user must have privileges sufficient to set restricted session variables. SeeSection 7.1.9.1, “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.
  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 anyNULL 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:

  • 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 asfull), except forBLOB andTEXT 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 ofNDB tables.
    The default value is full.
    When using minimal ornoblob, 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 source and replica silently diverge, thus breaking consistency.
    Setting this variable has no effect when the binary logging format is STATEMENT. Whenbinlog_format isMIXED, the setting forbinlog_row_image is applied to changes that are logged using row-based format, but this setting has 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

  Command-Line Format	--binlog-row-metadata=metadata_type
  System Variable	binlog_row_metadata
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Enumeration
  Default Value	MINIMAL
  Valid Values	FULL (All metadata is included)MINIMAL (Limit included metadata)
  Configures the amount of table metadata added to the binary log when using row-based logging. When set toMINIMAL, the default, only metadata related to SIGNED flags, column character set and geometry types are logged. When set toFULL complete metadata for tables is logged, such as column name,ENUM orSET string values, PRIMARY KEY information, and so on.
  The extended metadata serves the following purposes:

  • Replicas use the metadata to transfer data when its table structure is different from the source's.
  • External software can use the metadata to decode row events and store the data into external databases, such as a data warehouse.
• binlog_row_value_options

  Command-Line Format	--binlog-row-value-options=#
  System Variable	binlog_row_value_options
  Scope	Global, Session
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Set
  Default Value
  Valid Values	PARTIAL_JSON
  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 (seePartial Updates of JSON Values). This works for anUPDATE statement which modifies a JSON column using any sequence ofJSON_SET(),JSON_REPLACE(), andJSON_REMOVE(). If the server is unable to generate a partial update, the full document is used instead.
  The default value is an empty string, which disables use of the format. To unsetbinlog_row_value_options and revert to writing the full JSON document, set its value to the empty string.
  Setting the session value of this system variable is a restricted operation. The session user must have privileges sufficient to set restricted session variables. SeeSection 7.1.9.1, “System Variable Privileges”.
  binlog_row_value_options=PARTIAL_JSON takes effect only when binary logging is enabled andbinlog_format is set toROW or MIXED. Statement-based replication always logs only the modified parts of the JSON document, regardless of any value set forbinlog_row_value_options. To maximize the amount of space saved, usebinlog_row_image=NOBLOB orbinlog_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 replica. This includes a failure to find the path. Be aware that, even with this and other safety checks, if a JSON document on a replica has diverged from that on the source and a partial update is applied, it remains theoretically possible to produce a valid but unexpected JSON document on the replica.

• binlog_rows_query_log_events

  Command-Line Format	--binlog-rows-query-log-events[={OFF|ON}]
  System Variable	binlog_rows_query_log_events
  Scope	Global, Session
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Boolean
  Default Value	OFF
  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 source 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. SeeSection 7.1.9.1, “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

  Command-Line Format	--binlog-stmt-cache-size=#
  System Variable	binlog_stmt_cache_size
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value	32768
  Minimum Value	4096
  Maximum Value (64-bit platforms)	18446744073709547520
  Maximum Value (32-bit platforms)	4294963200
  Unit	bytes
  Block Size	4096
  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 thelog_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 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. TheBinlog_stmt_cache_use andBinlog_stmt_cache_disk_use status variables can be useful for tuning the size of this variable. See Section 7.4.4, “The Binary Log”.
  The binlog_cache_size system variable sets the size for the transaction cache.

• binlog_transaction_compression

  Command-Line Format	--binlog-transaction-compression[={OFF|ON}]
  System Variable	binlog_transaction_compression
  Scope	Global, Session
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Boolean
  Default Value	OFF
  Enables compression for transactions that are written to binary log files on this server. OFF is the default. Use thebinlog_transaction_compression_level_zstd system variable to set the level for thezstd algorithm that is used for compression.
  Settingbinlog_transaction_compression has no immediate effect but rather applies to all subsequentSTART REPLICA statements.
  When binary log transaction compression is enabled, transaction payloads are compressed and then written to the binary log file as a single event (Transaction_payload_event). Compressed transaction payloads remain in a compressed state while they are sent in the replication stream to replicas, other Group Replication group members, or clients such asmysqlbinlog, and are written to the relay log still in their compressed state. Binary log transaction compression therefore saves storage space both on the originator of the transaction and on the recipient (and for their backups), and saves network bandwidth when the transactions are sent between server instances.
  For binlog_transaction_compression=ON to have a direct effect, binary logging must be enabled on the server. When a MySQL 8.4 server instance has no binary log, it can receive, handle, and display compressed transaction payloads regardless of its value forbinlog_transaction_compression. Compressed transaction payloads received by such server instances are written in their compressed state to the relay log, so they benefit indirectly from compression carried out by other servers in the replication topology.
  This system variable cannot be changed within the context of a transaction. 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 7.1.9.1, “System Variable Privileges”.
  For more information on binary log transaction compression, including details of what events are and are not compressed, and changes in behavior when transaction compression is in use, seeSection 7.4.4.5, “Binary Log Transaction Compression”.
  You can use thendb_log_transaction_compression system variable to enable this feature forNDB. In addition, setting--binlog-transaction-compression=ON on the command line or in a my.cnf file causesndb_log_transaction_compression to be enabled on server startup. See the description of the variable for further information.

• binlog_transaction_compression_level_zstd

  Command-Line Format	--binlog-transaction-compression-level-zstd=#
  System Variable	binlog_transaction_compression_level_zstd
  Scope	Global, Session
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value	3
  Minimum Value	1
  Maximum Value	22
  Sets the compression level for binary log transaction compression on this server, which is enabled by thebinlog_transaction_compression system variable. The value is an integer that determines the compression effort, from 1 (the lowest effort) to 22 (the highest effort). If you do not specify this system variable, the compression level is set to 3.
  Settingbinlog_transaction_compression_level_zstd has no immediate effect but rather applies to all subsequentSTART REPLICA statements.
  As the compression level increases, the data compression ratio increases, which reduces the storage space and network bandwidth required for the transaction payload. However, the effort required for data compression also increases, taking time and CPU and memory resources on the originating server. Increases in the compression effort do not have a linear relationship to increases in the data compression ratio.
  This system variable cannot be changed within the context of a transaction. 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 7.1.9.1, “System Variable Privileges”.
  This variable has no effect on logging of transactions onNDB tables; usendb_log_transaction_compression_level_zstd instead.

• binlog_transaction_dependency_history_size

  Command-Line Format	--binlog-transaction-dependency-history-size=#
  System Variable	binlog_transaction_dependency_history_size
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value	25000
  Minimum Value	1
  Maximum Value	1000000
  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.

• log_bin

  System Variable	log_bin
  Scope	Global
  Dynamic	No
  SET_VAR Hint Applies	No
  Type	Boolean
  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. 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 toOFF. 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 7.4.4, “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. The maximum variable length is 256. In MySQL 8.4, if the --log-bin option is not supplied, the default base name isbinlog. 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_`hostname`_-bin, using the name of the host machine. The default location is the data directory.
• log_bin_index

  Command-Line Format	--log-bin-index=file_name
  System Variable	log_bin_index
  Scope	Global
  Dynamic	No
  SET_VAR Hint Applies	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. The maximum variable length is 256.

• log_bin_trust_function_creators

  Command-Line Format	--log-bin-trust-function-creators[={OFF|ON}]
  Deprecated	Yes
  System Variable	log_bin_trust_function_creators
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  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 may 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 theDETERMINISTIC characteristic, or with theREADS 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 27.7, “Stored Program Binary Logging”.

• log_replica_updates

  Command-Line Format	--log-replica-updates[={OFF|ON}]
  System Variable	log_replica_updates
  Scope	Global
  Dynamic	No
  SET_VAR Hint Applies	No
  Type	Boolean
  Default Value	ON
  log_replica_updates specifies whether updates received by a replica server from a replication source server should be logged to the replica's own binary log.
  Enabling this variable causes the replica to write the updates that are received from a source and performed by the replication SQL thread to the replica's own binary log. Binary logging, which is controlled by the--log-bin option and is enabled by default, must also be enabled on the replica for updates to be logged. SeeSection 19.1.6, “Replication and Binary Logging Options and Variables”.log_replica_updates is enabled by default, unless you specify--skip-log-bin to disable binary logging, in which case MySQL also disables replica update logging by default. If you need to disable replica update logging when binary logging is enabled, specify--log-replica-updates=OFF at replica server startup.
  Enablinglog_replica_updates enables replication servers to be chained. For example, you might want to set up replication servers using this arrangement:

A -> B -> C  

Here, A serves as the source for the replica B, and B serves as the source for the replica C. For this to work, B must be both a source_and_ a replica. With binary logging enabled andlog_replica_updates enabled, which are the default settings, updates received from A are logged by B to its binary log, and can therefore be passed on toC.

• log_slave_updates

  Command-Line Format	--log-slave-updates[={OFF|ON}]
  Deprecated	Yes
  System Variable	log_slave_updates
  Scope	Global
  Dynamic	No
  SET_VAR Hint Applies	No
  Type	Boolean
  Default Value	ON
  Deprecated alias forlog_replica_updates.

• log_statements_unsafe_for_binlog

  Command-Line Format	--log-statements-unsafe-for-binlog[={OFF|ON}]
  Deprecated	Yes
  System Variable	log_statements_unsafe_for_binlog
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Boolean
  Default Value	ON
  If error 1592 is encountered, controls whether the generated warnings are added to the error log or not.

• master_verify_checksum

  Command-Line Format	--master-verify-checksum[={OFF|ON}]
  Deprecated	Yes
  System Variable	master_verify_checksum
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Boolean
  Default Value	OFF
  Deprecated alias forsource_verify_checksum.

• max_binlog_cache_size

  Command-Line Format	--max-binlog-cache-size=#
  System Variable	max_binlog_cache_size
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value (64-bit platforms)	18446744073709547520
  Default Value (32-bit platforms)	4294967295
  Minimum Value	4096
  Maximum Value (64-bit platforms)	18446744073709547520
  Maximum Value (32-bit platforms)	4294967295
  Unit	bytes
  Block Size	4096
  If a transaction requires more than this many bytes, the server generates a Multi-statement transaction required more than 'max_binlog_cache_size' bytes of storage error. Whengtid_mode is notON, the maximum recommended value is 4GB, due to the fact that, in this case, MySQL cannot work with binary log positions greater than 4GB; whengtid_mode is ON, this limitation does not apply, and the server can work with binary log positions of arbitrary size.
  If, because gtid_mode is not ON, or for some other reason, you need to guarantee that the binary log does not exceed a given size maxsize, you should set this variable according to the formula shown here:

max_binlog_cache_size <  
  (((maxsize - max_binlog_size) / max_connections) - 1000) / 1.2  

This calculation takes into account the following conditions:

• The server writes to the binary log as long as the size before it begins to write is less thanmax_binlog_size.
• The server does not write single transactions, but rather groups of transactions. The maximum possible number of transactions in a group is equal tomax_connections.
• The server writes data that is not included in the cache. This includes a 4-byte checksum for each event; while this adds less than 20% to the transaction size, this amount is non-negible. In addition, the server writes a Gtid_log_event for each transaction; each of these events can add another 1 KB to what is written to the binary log.
  max_binlog_cache_size sets the size for the transaction cache only; the upper limit for the statement cache is governed by themax_binlog_stmt_cache_size system variable.
  The visibility to sessions ofmax_binlog_cache_size matches that of thebinlog_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

  Command-Line Format	--max-binlog-size=#
  System Variable	max_binlog_size
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value	1073741824
  Minimum Value	4096
  Maximum Value	1073741824
  Unit	bytes
  Block Size	4096
  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 inmax_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 thanmax_binlog_size.
  If max_relay_log_size is 0, the value ofmax_binlog_size applies to relay logs as well.
  With GTIDs in use on the server, whenmax_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 itsbinlog_error_action setting. If IGNORE_ERROR is set, an error is logged on the server and binary logging is halted, or ifABORT_SERVER is set, the server shuts down.

• max_binlog_stmt_cache_size

  Command-Line Format	--max-binlog-stmt-cache-size=#
  System Variable	max_binlog_stmt_cache_size
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value	18446744073709547520
  Minimum Value	4096
  Maximum Value	18446744073709547520
  Unit	bytes
  Block Size	4096
  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 themax_binlog_cache_size system variable.

• original_commit_timestamp
  For internal use by replication. When re-executing a transaction on a replica, this is set to the time when the transaction was committed on the original source, 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 either theREPLICATION_APPLIER privilege (see Section 19.3.3, “Replication Privilege Checks”), or privileges sufficient to set restricted session variables (see Section 7.1.9.1, “System Variable Privileges”). However, note that the variable is not intended for users to set; it is set automatically by the replication infrastructure.
• source_verify_checksum

  Command-Line Format	--source-verify-checksum[={OFF|ON}]
  System Variable	source_verify_checksum
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Boolean
  Default Value	OFF
  Enablingsource_verify_checksum causes the source to verify events read from the binary log by examining checksums, and to stop with an error in the event of a mismatch.source_verify_checksum is disabled by default; in this case, the source uses the event length from the binary log to verify events, so that only complete events are read from the binary log.

• sql_log_bin

  System Variable	sql_log_bin
  Scope	Session
  Dynamic	Yes
  SET_VAR Hint Applies	No
  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 isON. To disable or enable binary logging for the current session, set the sessionsql_log_bin variable toOFF or ON.
  Set this variable to OFF for a session to temporarily disable binary logging while making changes to the source you do not want replicated to the replica.
  Setting the session value of this system variable is a restricted operation. The session user must have privileges sufficient to set restricted session variables. SeeSection 7.1.9.1, “System Variable Privileges”.
  It is not possible to set the session value ofsql_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

  Command-Line Format	--sync-binlog=#
  System Variable	sync_binlog
  Scope	Global
  Dynamic	Yes
  SET_VAR Hint Applies	No
  Type	Integer
  Default Value	1
  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 afterN 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 tellmysqld 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.