All the details are written in the server in binary format. The Binary log is useful in the MySQL replication, where the main server will send data from binary logs to the remote servers. Basically, when we perform operations like creating the table or updating the data from the existing table these events details are stored in the binary logs. Start Your Free Data Science Course. Now let us create a table and perform an update on the table and see the binary log creation in the server.

Below let us get the last log that performed as in the above we are not able to read the binary log: —. This is a guide to MySQL Binlog. Here we discuss the Introduction to MySQL Binlog and the practical examples and different subquery expressions. When using statement-based logging, the following example does not work as you might expect. 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. To specify more than one database to ignore, use this option multiple times, once for each database.

You should not use this option if you are using cross-database updates and you do not want these updates to be logged. Checksum options. MySQL supports reading and writing of binary log checksums. These are enabled using the two options listed here:. Enabling this option causes the source 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. To control reading of checksums by the replica from the relay log , use the --slave-sql-verify-checksum option. Testing and debugging options. The following binary log options are used in replication testing and debugging. They are not intended for use in normal operations.

This option is used internally by the MySQL test suite for replication testing and debugging. The following list describes system variables for controlling binary logging.

They can be set at server startup and some of them can be changed at runtime using SET. Server options used to control binary logging are listed earlier in this section. The size of the memory buffer to hold changes to the binary log during a transaction. The block size is A value that is not an exact multiple of the block size is rounded down to the next lower multiple of the block size by MySQL Server before storing the value for the system variable.

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. 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. See The Binary Log. When enabled, this variable causes the source to write a checksum for each event in the binary log. The default is CRC If backward compatibility with older replicas is a concern, you may want to set the value explicitly to NONE.

Up to and including MySQL 8. 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. By default, this variable is disabled. As of MySQL 8. The session user must have privileges sufficient to set restricted session variables. See System Variable Privileges.

Otherwise, such statements are likely to cause the replica to diverge from the source. This variable has no effect when the binary log format is ROW or MIXED. 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 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. Previously encrypted files are not automatically decrypted, but the server is still able to read them.

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 Encrypting Binary Log Files and Relay Log Files. 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. On restart, recovery proceeds as in the case of an unexpected server halt see Section 3. This setting provides backward compatibility with older versions of MySQL.

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 MySQL Server Logs.

Beginning with MySQL 8. To remove binary log files manually, use the PURGE BINARY LOGS statement. See PURGE BINARY LOGS Statement. Enables or disables automatic purging of binary log files. Setting this variable to ON the default enables automatic purging; setting it to OFF disables automatic purging. This variable has no effect on PURGE BINARY LOGS.

This system variable sets the binary logging format, and can be any one of STATEMENT , ROW , or MIXED. See Section 5. 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 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 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, see 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. If any replication channel has open temporary tables, the replication format cannot be changed globally SET GLOBAL.

If any replication channel applier thread is currently running, the replication format cannot be changed globally SET GLOBAL. Trying to switch the replication format in any of these cases or attempting to set the current replication format results in an error. 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 using STATEMENT 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 to STATEMENT format for use in its own binary log, so this situation can cause replication to fail.

For more information, see 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.

Controls how many microseconds the binary log commit waits before synchronizing the binary log file to disk. 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.

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. 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.

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. 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. For more information on binary log encryption keys and the binary log master key, see Encrypting Binary Log Files and Relay Log Files. This global system variable is read-only and can be set only at server startup. 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. 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. When deleting a row, only the before image is logged, since there are no changed values to propagate following the deletion.

When inserting a row, only the after image is logged, since there is no existing row to be matched. Only when updating a row are both the before and after images required, and both written to the binary log. For the before image, it is necessary only that the minimum set of columns required to uniquely identify rows is logged. If the table containing the row has a primary key, then only the primary key column or columns are written to the binary log.

Otherwise, if the table has a unique key all of whose columns are NOT NULL , then only the columns in the unique key need be logged. If the table has neither a primary key nor a unique key without any NULL columns, then all columns must be used in the before image, and logged. In the after image, it is necessary to log only the columns which have actually changed. This variable actually takes one of three possible values, as shown in the following list:.

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

noblob : Log all columns same as full , except for BLOB and TEXT columns that are not required to identify rows, or that have not changed. This variable is not supported by NDB Cluster; setting it has no effect on the logging of NDB tables.

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

All columns must be present and in the same order; each column must use the same data type as its counterpart in the other table. For more information on binary log file and relay log file encryption, see Section 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. On restart, recovery proceeds as in the case of an unexpected server halt see Section This setting provides backward compatibility with older versions of MySQL.

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. Beginning with MySQL 8.

To remove binary log files manually, use the PURGE BINARY LOGS statement. See Section Enables or disables automatic purging of binary log files. Setting this variable to ON the default enables automatic purging; setting it to OFF disables automatic purging. This variable has no effect on PURGE BINARY LOGS. This system variable sets the binary logging format, and can be any one of STATEMENT , ROW , or MIXED. 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 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 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, see Section 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.

If any replication channel has open temporary tables, the replication format cannot be changed globally SET GLOBAL. If any replication channel applier thread is currently running, the replication format cannot be changed globally SET GLOBAL.

Trying to switch the replication format in any of these cases or attempting to set the current replication format results in an error. 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 using STATEMENT 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 to STATEMENT format for use in its own binary log, so this situation can cause replication to fail. For more information, see Section 5. 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. Controls how many microseconds the binary log commit waits before synchronizing the binary log file to disk.

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. 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.

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.

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.

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.

For more information on binary log encryption keys and the binary log master key, see Section This global system variable is read-only and can be set only at server startup.

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

For the before image, it is necessary only that the minimum set of columns required to uniquely identify rows is logged. If the table containing the row has a primary key, then only the primary key column or columns are written to the binary log. Otherwise, if the table has a unique key all of whose columns are NOT NULL , then only the columns in the unique key need be logged.

If the table has neither a primary key nor a unique key without any NULL columns, then all columns must be used in the before image, and logged. In the after image, it is necessary to log only the columns which have actually changed. This variable actually takes one of three possible values, as shown in the following list:. full : Log all columns in both the before image and the after image. minimal : Log only those columns in the before image that are required to identify the row to be changed; log only those columns in the after image where a value was specified by the SQL statement, or generated by auto-increment.

noblob : Log all columns same as full , except for BLOB and TEXT columns that are not required to identify rows, or that have not changed. This variable is not supported by NDB Cluster; setting it has no effect on the logging of NDB tables. When using minimal or noblob , deletes and updates are guaranteed to work correctly for a given table if and only if the following conditions are true for both the source and destination tables:.

All columns must be present and in the same order; each column must use the same data type as its counterpart in the other table. 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. 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. 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. 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. mysqlbinlog output includes partial JSON updates in the form of events encoded as base 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. 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.

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. The size of the memory buffer for the binary log to hold nontransactional statements issued during a transaction.

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. 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. Enables compression for transactions that are written to binary log files on this server. 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 as mysqlbinlog , 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. When a MySQL server instance has no binary log, if it is at a release from MySQL 8. 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. 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, see Section 5.

Prior to NDB 8. In NDB 8. See the description of the variable for further information. 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. 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.

It also contains events for statements that potentially could have made changes for example, a DELETE which matched no rows , unless row-based logging is used.

The binary log also contains information about how long each statement took that updated data. The binary log has two important purposes:. For replication, the binary log on a replication source server provides a record of the data changes to be sent to replicas. The source sends the information contained in its binary log to its replicas, which reproduce those transactions to make the same data changes that were made on the source. See Section Certain data recovery operations require use of the binary log.

After a backup has been restored, the events in the binary log that were recorded after the backup was made are re-executed. These events bring databases up to date from the point of the backup. See Section 7. The binary log is not used for statements such as SELECT or SHOW that do not modify data. To log all statements for example, to identify a problem query , use the general query log.

See Section 5. Running a server with binary logging enabled makes performance slightly slower. However, the benefits of the binary log in enabling you to set up replication and for restore operations generally outweigh this minor performance decrement. The binary log is resilient to unexpected halts.

Only complete events or transactions are logged or read back. Passwords in statements written to the binary log are rewritten by the server not to occur literally in plain text. See also Section 6. From MySQL 8. For more information, see Section The following discussion describes some of the server options and variables that affect the operation of binary logging. For a complete list, see Section 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, but can be enabled by specifying the --log-bin option.

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. The --log-slave-updates and --slave-preserve-commit-order options require binary logging. 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.

If you do not supply the --log-bin option, MySQL uses binlog as the default base name for the binary log files. It is recommended that you specify a base name, so that if the host name changes, you can easily continue to use the same binary log file names see Section B. extension , the extension is silently removed and ignored. mysqld appends a numeric extension to the binary log base name to generate binary log file names.

The number increases each time the server creates a new log file, thus creating an ordered series of files. The server creates a new file in the series each time any of the following events occurs:. To keep track of which binary log files have been used, mysqld also creates a binary log index file that contains the names of the binary log files.

By default, this has the same base name as the binary log file, with the extension '. You should not manually edit this file while mysqld is running; doing so would confuse mysqld. The default location for binary log files and the binary log index file 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.

In MySQL 5. In MySQL 8. For servers that are used in a replication topology, you must specify a unique nonzero server ID for each server. A client that has privileges sufficient to set restricted session system variables see Section 5. By default, the server logs the length of the event as well as the event itself and uses this to verify that the event was written correctly.

The format of the events recorded in the binary log is dependent on the binary logging format. Three format types are supported: row-based logging, statement-based logging and mixed-base logging. The binary logging format used depends on the MySQL version. For general descriptions of the logging formats, see Section 5. For detailed information about the format of the binary log, see MySQL Internals: The Binary Log. The server evaluates the --binlog-do-db and --binlog-ignore-db options in the same way as it does the --replicate-do-db and --replicate-ignore-db options.

For information about how this is done, see Section The binary log must be enabled for this setting to work see Section This setting enables the replica to act as a source to other replicas. You can delete all binary log files with the RESET MASTER statement, or a subset of them with PURGE BINARY LOGS. If you are using replication, you should not delete old binary log files on the source until you are sure that no replica still needs to use them.

For example, if your replicas never run more than three days behind, once a day you can execute mysqladmin flush-logs binary on the source and then remove any logs that are more than three days old.

You can remove the files manually, but it is preferable to use PURGE BINARY LOGS , which also safely updates the binary log index file for you and which can take a date argument. You can display the contents of binary log files with the mysqlbinlog utility. This can be useful when you want to reprocess statements in the log for a recovery operation. For example, you can update a MySQL server from the binary log as follows:. mysqlbinlog also can be used to display the contents of the relay log file on a replica, because they are written using the same format as binary log files.

For more information on the mysqlbinlog utility and how to use it, see Section 4. For more information about the binary log and recovery operations, see Section 7. Binary logging is done immediately after a statement or transaction completes but before any locks are released or any commit is done. This ensures that the log is logged in commit order. Updates to nontransactional tables are stored in the binary log immediately after execution.

Within an uncommitted transaction, all updates UPDATE , DELETE , or INSERT that change transactional tables such as InnoDB tables are cached until a COMMIT statement is received by the server. At that point, mysqld writes the entire transaction to the binary log before the COMMIT is executed.

Modifications to nontransactional tables cannot be rolled back. If a transaction that is rolled back includes modifications to nontransactional tables, the entire transaction is logged with a ROLLBACK statement at the end to ensure that the modifications to those tables are replicated. If a statement is bigger than this, the thread opens a temporary file to store the transaction. The temporary file is deleted when the thread ends. If a transaction is larger than this many bytes, it fails and rolls back.

The minimum value is If you are using the binary log and row based logging, concurrent inserts are converted to normal inserts for CREATE SELECT or INSERT SELECT statements. This is done to ensure that you can re-create an exact copy of your tables by applying the log during a backup operation. If you are using statement-based logging, the original statement is written to the log.

The binary log format has some known limitations that can affect recovery from backups. Binary logging for stored programs is done as described in Section Note that the binary log format differs in MySQL 8. If the server is unable to write to the binary log, flush binary log files, or synchronize the binary log to disk, the binary log on the replication source server can become inconsistent and replicas can lose synchronization with the source.

At this point, you can identify and correct the cause of the error. On restart, recovery proceeds as in the case of an unexpected server halt see Section With this setting, the server continues the ongoing transaction and logs the error, then halts binary logging, but continues to perform updates.

Only use this option if you require backward compatibility, and the binary log is non-essential on this MySQL server instance. For example, you might use the binary log only for intermittent auditing or debugging of the server, and not use it for replication from the server or rely on it for point-in-time restore operations. For example, if you are using InnoDB tables and the MySQL server processes a COMMIT statement, it writes many prepared transactions to the binary log in sequence, synchronizes the binary log, and then commits the transaction into InnoDB.

If the server unexpectedly exited between those two operations, the transaction would be rolled back by InnoDB at restart but still exist in the binary log. Such an issue was resolved in previous releases by enabling InnoDB support for two-phase commit in XA transactions. InnoDB support for two-phase commit in XA transactions ensures that the binary log and InnoDB data files are synchronized.

However, the MySQL server should also be configured to synchronize the binary log and the InnoDB logs to disk before committing the transaction. The MySQL server then tells InnoDB to complete any prepared transactions that were successfully written to the to the binary log, and truncates the binary log to the last valid position. This ensures that the binary log reflects the exact data of InnoDB tables, and therefore the replica remains in synchrony with the source because it does not receive a statement which has been rolled back.

Binary Logging Options and Variables. If an event cannot be split, the maximum size can be exceeded. IF EXISTS Statements. If error is encountered, controls whether the generated warnings are added to the error log or not. Replication and Source or Replica Shutdowns.

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