MySQL 5.6 Reference Manual Including MySQL NDB Cluster 7.3-7.4 Reference Guide
You can use the mysqld options and system variables that are described in this section to affect the operation of the binary log as well as to control which statements are written to the binary log. For additional information about the binary log, see Section 5.4.4, “The Binary Log”. For additional information about using MySQL server options and system variables, see Section 5.1.6, “Server Command Options”, and Section 5.1.7, “Server System Variables”.
The following list describes startup options for enabling and configuring the binary log. System variables used with binary logging are discussed later in this section.
Command-Line Format | --binlog-row-event-max-size=# |
---|---|
Type | Integer |
Default Value | 8192 |
Minimum Value | 256 |
Maximum Value (64-bit platforms) | 18446744073709551615 |
Maximum Value (32-bit platforms) | 4294967295 |
Specify the maximum size of a row-based binary log event, in bytes. Rows are grouped into events smaller than this size if possible. The value should be a multiple of 256. See Section 17.1.2, “Replication Formats”.
Command-Line Format | --log-bin=file_name |
---|---|
Type | File name |
Enables binary logging. With binary logging enabled, the server logs all statements that change data to the binary log, which is used for backup and replication. The binary log is a sequence of files with a base name and numeric extension. For information on the format and management of the binary log, see Section 5.4.4, “The Binary Log”.
The option value, if given, is the base name for the log
sequence. The server creates binary log files in sequence by
adding a numeric suffix to the base name. It is recommended
that you specify a base name (see
Section B.3.7, “Known Issues in MySQL”, for the reason). Otherwise,
MySQL uses
as the base name.
host_name
-bin
If you supply a value for the --log-bin
option, the value is used as the base name for the log
sequence. The server creates binary log files in sequence by
adding a numeric suffix to the base name. In MySQL 5.6, the
default base name is the name of the process ID file, with
the suffix -bin
. That name can be set
with the --pid-file
option,
and it defaults to the name of the host machine. It is
recommended that you specify a base name using the
--log-bin
option, so that you can continue
to use the same binary log file names regardless of changes
to the default name.
The default location for binary log files is the data
directory. You can use the --log-bin
option
to specify an alternative location, by adding a leading
absolute path name to the base name to specify a different
directory. When the server reads an entry from the binary
log index file, which tracks the binary log files that have
been used, it checks whether the entry contains a relative
path. If it does, the relative part of the path is replaced
with the absolute path set using the
--log-bin
option. An absolute path recorded
in the binary log index file remains unchanged; in such a
case, the index file must be edited manually to enable a new
path or paths to be used. (In older versions of MySQL,
manual intervention was required whenever relocating the
binary log or relay log files.) (Bug #11745230, Bug #12133)
Setting this option causes the
log_bin
system variable to
be set to ON
(or 1
),
and not to the base name. The binary log file base name and
any specified path are available as the
log_bin_basename
system
variable.
If you want to disable binary logging for a server start but
keep the --log-bin
setting intact, you can
specify the
--skip-log-bin
or
--disable-log-bin
option at startup. Specify the option after the
--log-bin
option, so that it takes
precedence. When binary logging is disabled, the
log_bin
system variable is
set to OFF.
Command-Line Format | --log-bin-index=file_name |
---|---|
System Variable | log_bin_index |
Scope | Global |
Dynamic | No |
Type | File name |
The name for the binary log index file, which contains the
names of the binary log files. By default, it has the same
location and base name as the value specified for the binary
log files using the --log-bin
option, plus the extension .index
. If
you do not specify --log-bin
,
the default binary log index file name is
binlog.index
. If you omit the file name
and do not specify one with
--log-bin
, the default binary
log index file name is
,
using the name of the host machine.
host_name
-bin.index
For information on the format and management of the binary log, see Section 5.4.4, “The Binary Log”.
Statement selection options. The options in the following list affect which statements are written to the binary log, and thus sent by a replication source server to its replicas. There are also options for replica servers that control which statements received from the source should be executed or ignored. For details, see Section 17.1.4.3, “Replica Server Options and Variables”.
Command-Line Format | --binlog-do-db=name |
---|---|
Type | String |
This option affects binary logging in a manner similar to
the way that
--replicate-do-db
affects
replication.
The effects of this option depend on whether the
statement-based or row-based logging format is in use, in
the same way that the effects of
--replicate-do-db
depend on
whether statement-based or row-based replication is in use.
You should keep in mind that the format used to log a given
statement may not necessarily be the same as that indicated
by the value of
binlog_format
. For example,
DDL statements such as CREATE
TABLE
and ALTER
TABLE
are always logged as statements, without
regard to the logging format in effect, so the following
statement-based rules for --binlog-do-db
always apply in determining whether or not the statement is
logged.
Statement-based logging.
Only those statements are written to the binary log where
the default database (that is, the one selected by
USE
) is
db_name
. To specify more than
one database, use this option multiple times, once for
each database; however, doing so does
not cause cross-database statements
such as UPDATE
to be logged while a different
database (or no database) is selected.
some_db.some_table
SET
foo='bar'
To specify multiple databases you must use multiple instances of this option. Because database names can contain commas, the list is treated as the name of a single database if you supply a comma-separated list.
An example of what does not work as you might expect when
using statement-based logging: If the server is started with
--binlog-do-db=sales
and you
issue the following statements, the
UPDATE
statement is
not logged:
USE prices; UPDATE sales.january SET amount=amount+1000;
The main reason for this “just check the default
database” behavior is that it is difficult from the
statement alone to know whether it should be replicated (for
example, if you are using multiple-table
DELETE
statements or
multiple-table UPDATE
statements that act across multiple databases). It is also
faster to check only the default database rather than all
databases if there is no need.
Another case which may not be self-evident occurs when a
given database is replicated even though it was not
specified when setting the option. If the server is started
with --binlog-do-db=sales
, the following
UPDATE
statement is logged
even though prices
was not included when
setting --binlog-do-db
:
USE sales; UPDATE prices.discounts SET percentage = percentage + 10;
Because sales
is the default database
when the UPDATE
statement is
issued, the UPDATE
is logged.
Row-based logging.
Logging is restricted to database
db_name
. Only changes to tables
belonging to db_name
are
logged; the default database has no effect on this.
Suppose that the server is started with
--binlog-do-db=sales
and
row-based logging is in effect, and then the following
statements are executed:
USE prices; UPDATE sales.february SET amount=amount+100;
The changes to the february
table in the
sales
database are logged in accordance
with the UPDATE
statement;
this occurs whether or not the
USE
statement was issued.
However, when using the row-based logging format and
--binlog-do-db=sales
, changes
made by the following UPDATE
are not logged:
USE prices; UPDATE prices.march SET amount=amount-25;
Even if the USE prices
statement were
changed to USE sales
, the
UPDATE
statement's
effects would still not be written to the binary log.
Another important difference in
--binlog-do-db
handling for
statement-based logging as opposed to the row-based logging
occurs with regard to statements that refer to multiple
databases. Suppose that the server is started with
--binlog-do-db=db1
, and the
following statements are executed:
USE db1; UPDATE db1.table1, db2.table2 SET db1.table1.col1 = 10, db2.table2.col2 = 20;
If you are using statement-based logging, the updates to
both tables are written to the binary log. However, when
using the row-based format, only the changes to
table1
are logged;
table2
is in a different database, so it
is not changed by the UPDATE
.
Now suppose that, instead of the USE db1
statement, a USE db4
statement had been
used:
USE db4; UPDATE db1.table1, db2.table2 SET db1.table1.col1 = 10, db2.table2.col2 = 20;
In this case, the UPDATE
statement is not written to the binary log when using
statement-based logging. However, when using row-based
logging, the change to table1
is logged,
but not that to table2
—in other
words, only changes to tables in the database named by
--binlog-do-db
are logged,
and the choice of default database has no effect on this
behavior.
Command-Line Format | --binlog-ignore-db=name |
---|---|
Type | String |
This option affects binary logging in a manner similar to
the way that
--replicate-ignore-db
affects
replication.
The effects of this option depend on whether the
statement-based or row-based logging format is in use, in
the same way that the effects of
--replicate-ignore-db
depend
on whether statement-based or row-based replication is in
use. You should keep in mind that the format used to log a
given statement may not necessarily be the same as that
indicated by the value of
binlog_format
. For example,
DDL statements such as CREATE
TABLE
and ALTER
TABLE
are always logged as statements, without
regard to the logging format in effect, so the following
statement-based rules for
--binlog-ignore-db
always apply in
determining whether or not the statement is logged.
Statement-based logging.
Tells the server to not log any statement where the
default database (that is, the one selected by
USE
) is
db_name
.
Prior to MySQL 5.6.12, this option caused any statements
containing fully qualified table names not to be logged if
there was no default database specified (that is, when
SELECT
DATABASE()
returned
NULL
). In MySQL 5.6.12 and higher, when
there is no default database, no
--binlog-ignore-db
options are applied, and
such statements are always logged. (Bug #11829838, Bug
#60188)
Row-based format.
Tells the server not to log updates to any tables in the
database db_name
. The current
database has no effect.
When using statement-based logging, the following example
does not work as you might expect. Suppose that the server
is started with
--binlog-ignore-db=sales
and
you issue the following statements:
USE prices; UPDATE sales.january SET amount=amount+1000;
The UPDATE
statement
is logged in such a case because
--binlog-ignore-db
applies
only to the default database (determined by the
USE
statement). Because the
sales
database was specified explicitly
in the statement, the statement has not been filtered.
However, when using row-based logging, the
UPDATE
statement's
effects are not written to the binary
log, which means that no changes to the
sales.january
table are logged; in this
instance,
--binlog-ignore-db=sales
causes all changes made to tables in
the source'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 is treated as the name of a single database if you supply a comma-separated list.
You should not use this option if you are using cross-database updates and you do not want these updates to be logged.
Checksum options. MySQL supports reading and writing of binary log checksums. These are enabled using the two options listed here:
--binlog-checksum={NONE|CRC32}
Command-Line Format | --binlog-checksum=type |
---|---|
Type | String |
Default Value | CRC32 |
Valid Values |
|
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.
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.
Command-Line Format | --max-binlog-dump-events=# |
---|---|
Type | Integer |
Default Value | 0 |
This option is used internally by the MySQL test suite for replication testing and debugging.
Command-Line Format | --sporadic-binlog-dump-fail[={OFF|ON}] |
---|---|
Type | Boolean |
Default Value | OFF |
This option is used internally by the MySQL test suite for replication testing and debugging.
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.
Command-Line Format | --binlog-cache-size=# |
---|---|
System Variable | binlog_cache_size |
Scope | Global |
Dynamic | Yes |
Type | Integer |
Default Value | 32768 |
Minimum Value | 4096 |
Maximum Value (64-bit platforms) | 18446744073709551615 |
Maximum Value (32-bit platforms) | 4294967295 |
The size of the cache to hold changes to the binary log
during a transaction. A binary log cache is allocated for
each client if the server supports any transactional storage
engines and if the server has the binary log enabled
(--log-bin
option). If you
often use large transactions, you can increase this cache
size to get better performance. The
Binlog_cache_use
and
Binlog_cache_disk_use
status variables can be useful for tuning the size of this
variable. See Section 5.4.4, “The Binary Log”.
binlog_cache_size
sets the size for the
transaction cache only; the size of the statement cache is
governed by the
binlog_stmt_cache_size
system variable.
Command-Line Format | --binlog-checksum=name |
---|---|
System Variable | binlog_checksum |
Scope | Global |
Dynamic | Yes |
Type | String |
Default Value | CRC32 |
Valid Values |
|
When enabled, this variable causes the replication source
server to write a checksum for each event in the binary log.
binlog_checksum
supports the values
NONE
(disabled) and
CRC32
. The default is
CRC32
.
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 source to a value unrecognized
by the replica causes the replica 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 replicas is a concern, you may want to set the
value explicitly to NONE
.
binlog_direct_non_transactional_updates
Command-Line Format | --binlog-direct-non-transactional-updates[={OFF|ON}] |
---|---|
System Variable | binlog_direct_non_transactional_updates |
Scope | Global, Session |
Dynamic | Yes |
Type | Boolean |
Default Value | OFF |
Due to concurrency issues, a 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.
The
binlog_direct_non_transactional_updates
variable offers one possible workaround to this issue. By
default, this variable is disabled. Enabling
binlog_direct_non_transactional_updates
causes updates to nontransactional tables to be written
directly to the binary log, rather than to the transaction
cache.
binlog_direct_non_transactional_updates
works only for statements that are replicated using the
statement-based binary logging format; that is,
it works only when the value of
binlog_format
is
STATEMENT
, or when
binlog_format
is
MIXED
and a given statement is being
replicated using the statement-based format. This variable
has no effect when the binary log format is
ROW
, or when
binlog_format
is set to
MIXED
and a given statement is replicated
using the row-based format.
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.
In MySQL 5.6, this variable has no effect when
the binary log format is ROW
or
MIXED
. (Bug #51291)
Command-Line Format | --binlog-error-action[=value] |
---|---|
Introduced | 5.6.22 |
System Variable | binlog_error_action |
Scope | Global |
Dynamic | Yes |
Type | Enumeration |
Default Value | IGNORE_ERROR |
Valid Values |
|
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.
In MySQL 5.6, this variable defaults to
IGNORE_ERROR
. If the server encounters
such an error, it continues the ongoing transaction, logs
the error then halts logging, and continues performing
updates. To resume binary logging
log_bin
must be enabled
again, which requires a server restart. This setting
provides backward compatibility with older versions of
MySQL.
Setting this variable to ABORT_SERVER
makes the server halt logging and shut down whenever it
encounters such an error with the binary log. On restart,
recovery proceeds as in the case of an unexpected server
halt (see
Section 17.3.2, “Handling an Unexpected Halt of a Replica Server”).
This is the recommended setting, particularly in complex
replication environments.
In previous releases this variable was named
binlogging_impossible_mode
.
Command-Line Format | --binlog-format=format |
---|---|
System Variable | binlog_format |
Scope | Global, Session |
Dynamic | Yes |
Type | Enumeration |
Default Value (≥ 5.6.10-ndb-7.3.1) | MIXED |
Default Value | STATEMENT |
Valid Values |
|
This variable sets the binary logging format, and can be any
one of STATEMENT
, ROW
,
or MIXED
. See
Section 17.1.2, “Replication Formats”.
binlog_format
can be set at
startup or at runtime, except that under some conditions,
changing this variable at runtime is not possible or causes
replication to fail, as described later.
In MySQL 5.6, the default format is
STATEMENT
.
Exception: In MySQL NDB Cluster 7.3 and
later, the default is MIXED
;
statement-based replication is not supported for NDB
Cluster.
Setting the session value of this system variable is a restricted operation. The session user must have privileges sufficient to set restricted session variables. See Section 5.1.8.1, “System Variable Privileges”.
The rules governing when changes to this variable take effect and how long the effect lasts are the same as for other MySQL server system variables. For more information, see Section 13.7.4.1, “SET Syntax for Variable Assignment”.
When MIXED
is specified, statement-based
replication is used, except for cases where only row-based
replication is guaranteed to lead to proper results. For
example, this happens when statements contain user-defined
functions (UDF) or the UUID()
function.
For details of how stored programs (stored procedures and functions, triggers, and events) are handled when each binary logging format is set, see Section 20.7, “Stored Program Binary Logging”.
There are exceptions when you cannot switch the replication format at runtime:
From within a stored function or a trigger.
If the session is currently in row-based replication mode and has open temporary tables.
From within a transaction.
Trying to switch the format in those cases results in an error.
Changing the logging format on a replication 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 5.4.4.2, “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.
Command-Line Format | --binlogging-impossible-mode[=value] |
---|---|
Introduced | 5.6.20 |
Deprecated | 5.6.22 |
System Variable | binlogging_impossible_mode |
Scope | Global, Session |
Dynamic | Yes |
Type | Enumeration |
Default Value | IGNORE_ERROR |
Valid Values |
|
This option is deprecated; expect it to be removed in a
future MySQL release. Use the
binlog_error_action
variable to control what happens when the server cannot
write to the binary log.
Command-Line Format | --binlog-max-flush-queue-time=# |
---|---|
System Variable | binlog_max_flush_queue_time |
Scope | Global |
Dynamic | Yes |
Type | Integer |
Default Value | 0 |
Minimum Value | 0 |
Maximum Value | 100000 |
How long in microseconds to keep reading transactions from
the flush queue before proceeding with the group commit (and
syncing the log to disk, if
sync_binlog
is greater than
0). If the value is 0 (the default), there is no timeout and
the server keeps reading new transactions until the queue is
empty.
Normally,
binlog_max_flush_queue_time
can remain set to 0. If the server processes a large number
of connections (for example, 100 or more) and many short
transactions with low-latency requirements, it may be useful
to set the value larger than 0 to force more frequent
flushes to disk.
Command-Line Format | --binlog-order-commits[={OFF|ON}] |
---|---|
System Variable | binlog_order_commits |
Scope | Global |
Dynamic | Yes |
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. 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.
Command-Line Format | --binlog-row-image=image_type |
---|---|
System Variable | binlog_row_image |
Scope | Global, Session |
Dynamic | Yes |
Type | Enumeration |
Default Value | full |
Valid Values |
|
For MySQL row-based replication, this variable determines how row images are written to the binary log.
In MySQL row-based replication, each row change event contains two images, a “before” image whose columns are matched against when searching for the row to be updated, and an “after” image containing the changes. Normally, MySQL logs full rows (that is, all columns) for both the before and after images. However, it is not strictly necessary to include every column in both images, and we can often save disk, memory, and network usage by logging only those columns which are actually required.
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.
You can cause the server to log full or minimal rows using
the binlog_row_image
system variable.
This variable actually takes one of three possible values,
as shown in the following list:
full
: Log all columns in both the
before image and the after image.
minimal
: Log only those columns in
the before image that are required to identify the row
to be changed; log only those columns in the after image
where a value was specified by the SQL statement, or
generated by auto-increment.
noblob
: Log all columns (same as
full
), except for
BLOB
and
TEXT
columns that are not
required to identify rows, or that have not changed.
This variable is not supported by NDB Cluster; setting it
has no effect on the logging of
NDB
tables. (Bug #16316828)
The default value is full
.
When using minimal
or
noblob
, deletes and updates are
guaranteed to work correctly for a given table if and only
if the following conditions are true for both the source and
destination tables:
All columns must be present and in the same order; each column must use the same data type as its counterpart in the other table.
The tables must have identical primary key definitions.
(In other words, the tables must be identical with the possible exception of indexes that are not part of the tables' primary keys.)
If these conditions are not met, it is possible that the primary key column values in the destination table may prove insufficient to provide a unique match for a delete or update. In this event, no warning or error is issued; the source and replica 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 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.
Command-Line Format | --binlog-rows-query-log-events[={OFF|ON}] |
---|---|
System Variable | binlog_rows_query_log_events |
Scope | Global, Session |
Dynamic | Yes |
Type | Boolean |
Default Value | OFF |
This system variable affects row-based logging only. When enabled, it causes 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
.
Command-Line Format | --binlog-stmt-cache-size=# |
---|---|
System Variable | binlog_stmt_cache_size |
Scope | Global |
Dynamic | Yes |
Type | Integer |
Default Value | 32768 |
Minimum Value | 4096 |
Maximum Value (64-bit platforms) | 18446744073709551615 |
Maximum Value (32-bit platforms) | 4294967295 |
This variable determines the size of the cache for the
binary log to hold nontransactional statements issued during
a transaction. Separate binary log transaction and statement
caches are allocated for each client if the server supports
any transactional storage engines and if the server has the
binary log enabled (--log-bin
option). If you often use large nontransactional statements
during transactions, you can increase this cache size to get
better performance. The
Binlog_stmt_cache_use
and
Binlog_stmt_cache_disk_use
status variables can be useful for tuning the size of this
variable. See Section 5.4.4, “The Binary Log”.
The binlog_cache_size
system variable sets the size for the transaction cache.
Command-Line Format | --expire-logs-days=# |
---|---|
System Variable | expire_logs_days |
Scope | Global |
Dynamic | Yes |
Type | Integer |
Default Value | 0 |
Minimum Value | 0 |
Maximum Value | 99 |
The number of days for automatic binary log file removal. The default is 0, which means “no automatic removal.” Possible removals happen at startup and when the binary log is flushed. Log flushing occurs as indicated in Section 5.4, “MySQL Server Logs”.
To remove binary log files manually, use the
PURGE BINARY LOGS
statement.
See Section 13.4.1.1, “PURGE BINARY LOGS Statement”.
System Variable | log_bin |
---|---|
Scope | Global |
Dynamic | No |
Type | Boolean |
Whether the binary log is enabled. If the
--log-bin
option is used,
then the value of this variable is ON
;
otherwise it is OFF
. This variable
reports only on the status of binary logging (enabled or
disabled); it does not actually report the value to which
--log-bin
is set.
System Variable | log_bin_basename |
---|---|
Scope | Global |
Dynamic | No |
Type | File name |
Holds the base name and path for the binary log files, which
can be set with the --log-bin
server option. The maximum variable length is 256. In MySQL
5.6, the default base name is the name of the process ID
file, with the suffix -bin
. That name can
be set with the --pid-file
option, and it defaults to the name of the host machine. The
default location for the binary log files is the data
directory.
Command-Line Format | --log-bin-index=file_name |
---|---|
System Variable | log_bin_index |
Scope | Global |
Dynamic | 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}] |
---|---|
System Variable | log_bin_trust_function_creators |
Scope | Global |
Dynamic | Yes |
Type | Boolean |
Default Value | OFF |
This variable applies when binary logging is enabled. It
controls whether stored function creators can be trusted not
to create stored functions that cause unsafe events to be
written to the binary log. If set to 0 (the default), users
are not permitted to create or alter stored functions unless
they have the SUPER
privilege
in addition to the CREATE
ROUTINE
or ALTER
ROUTINE
privilege. A setting of 0 also enforces
the restriction that a function must be declared with the
DETERMINISTIC
characteristic, or with the
READS SQL DATA
or NO
SQL
characteristic. If the variable is set to 1,
MySQL does not enforce these restrictions on stored function
creation. This variable also applies to trigger creation.
See Section 20.7, “Stored Program Binary Logging”.
Command-Line Format | --log-bin-use-v1-row-events[={OFF|ON}] |
---|---|
System Variable | log_bin_use_v1_row_events |
Scope | Global |
Dynamic | No |
Type | Boolean |
Default Value | OFF |
Whether Version 2 binary logging is in use. If this variable is 0 (disabled, the default), Version 2 binary log events are in use. If this variable is 1 (enabled), the server writes the binary log using Version 1 logging events (the only version of binary log events used in previous releases), and thus produces a binary log that can be read by older replicas.
MySQL 5.6 uses Version 2 binary log row events
by default. However, Version 2 events cannot be read by
MySQL Server releases prior to MySQL 5.6.6. Enabling
log_bin_use_v1_row_events
causes mysqld to write the binary log
using Version 1 logging events.
This variable is read-only at runtime. To switch between
Version 1 and Version 2 binary event binary logging, it is
necessary to set
log_bin_use_v1_row_events
at server startup.
Other than when performing upgrades of NDB Cluster
Replication,
log_bin_use_v1_row_events
is chiefly of interest when setting up replication conflict
detection and resolution using
NDB$EPOCH_TRANS()
as the conflict
detection function, which requires Version 2 binary log row
events. Thus, this variable and
--ndb-log-transaction-id
are
not compatible.
MySQL NDB Cluster 7.3 and higher use Version 2 binary log row events by default. You should keep this mind when planning upgrades or downgrades, and for setups using NDB Cluster Replication.
For more information, see Section 18.6.11, “NDB Cluster Replication Conflict Resolution”.
Command-Line Format | --log-slave-updates[={OFF|ON}] |
---|---|
System Variable | log_slave_updates |
Scope | Global |
Dynamic | No |
Type | Boolean |
Default Value | OFF |
Whether updates received by a replica from a replication source server should be logged to the replica's own binary log.
Normally, a replica does not log to its own binary log any
updates that are received from a source. Enabling this
variable causes the replica to write the updates performed
by its replication SQL thread to its own binary log. For
this option to have any effect, the replica must also be
started with the --log-bin
option to enable binary logging. See
Section 17.1.4, “Replication and Binary Logging Options and Variables”. A warning is issued
if you enable
log_slave_updates
without
also starting the server with the
--log-bin
option.
log_slave_updates
is
enabled when you want to chain replication servers. For
example, you might want to set up replication servers using
this arrangement:
A -> B -> C
Here, A
serves as the 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. You must start both
A
and B
with
--log-bin
to enable binary
logging, and B
with
log_slave_updates
enabled
so that updates received from A
are
logged by B
to its binary log.
Command-Line Format | --master-verify-checksum[={OFF|ON}] |
---|---|
System Variable | master_verify_checksum |
Scope | Global |
Dynamic | Yes |
Type | Boolean |
Default Value | OFF |
Enabling this variable 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.
master_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.
Command-Line Format | --max-binlog-cache-size=# |
---|---|
System Variable | max_binlog_cache_size |
Scope | Global |
Dynamic | Yes |
Type | Integer |
Default Value | 18446744073709551615 |
Minimum Value | 4096 |
Maximum Value | 18446744073709551615 |
If a transaction requires more than this many bytes of memory, the server generates a Multi-statement transaction required more than 'max_binlog_cache_size' bytes of storage error. The minimum value is 4096. The maximum possible value is 16EB (exabytes). The maximum recommended value is 4GB; this is due to the fact that MySQL currently cannot work with binary log positions greater than 4GB.
max_binlog_cache_size
sets the size for
the transaction cache only; the upper limit for the
statement cache is governed by the
max_binlog_stmt_cache_size
system variable.
In MySQL 5.6, the visibility to sessions of
max_binlog_cache_size
matches that of the
binlog_cache_size
system
variable; in other words, changing its value effects only
new sessions that are started after the value is changed.
Command-Line Format | --max-binlog-size=# |
---|---|
System Variable | max_binlog_size |
Scope | Global |
Dynamic | Yes |
Type | Integer |
Default Value | 1073741824 |
Minimum Value | 4096 |
Maximum Value | 1073741824 |
If a write to the binary log causes the current log file size to exceed the value of this variable, the server rotates the binary logs (closes the current file and opens the next one). The minimum value is 4096 bytes. The maximum and default value is 1GB.
A transaction is written in one chunk to the binary log, so
it is never split between several binary logs. Therefore, if
you have big transactions, you might see binary log files
larger than
max_binlog_size
.
If max_relay_log_size
is 0,
the value of
max_binlog_size
applies to
relay logs as well.
Command-Line Format | --max-binlog-stmt-cache-size=# |
---|---|
System Variable | max_binlog_stmt_cache_size |
Scope | Global |
Dynamic | Yes |
Type | Integer |
Default Value | 18446744073709547520 |
Minimum Value | 4096 |
Maximum Value | 18446744073709547520 |
If nontransactional statements within a transaction require more than this many bytes of memory, the server generates an error. The minimum value is 4096. The maximum and default values are 4GB on 32-bit platforms and 16EB (exabytes) on 64-bit platforms.
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.
System Variable | sql_log_bin |
---|---|
Scope | Session |
Dynamic | Yes |
Type | Boolean |
Default Value | ON |
This variable controls whether logging to the binary log is
enabled for the current session (assuming that the binary
log itself is enabled). The default value is
ON
. To disable or enable binary logging
for the current session, set the session
sql_log_bin
variable to
OFF
or ON
.
Set this variable to OFF
for a session to
temporarily disable binary logging while making changes to
the 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. See Section 5.1.8.1, “System Variable Privileges”.
It is not possible to set the session value of
sql_log_bin
within a
transaction or subquery.
Setting this variable to OFF
prevents GTIDs from being assigned to transactions in the
binary log. If you are using GTIDs for
replication, this means that, even when binary logging is
later enabled once again, the GTIDs written into the log
from this point do not account for any transactions that
occurred in the meantime—in effect, those transactions
are lost.
As of MySQL 5.6.22, the global
sql_log_bin
variable is
read only and cannot be modified. The global scope is
deprecated; expect it to be removed in a future MySQL
release. Prior to 5.6.22,
sql_log_bin
can be set as a
global or session variable. Setting
sql_log_bin
globally is
only detected when a new session is started. Any sessions
previously running are not impacted when setting
sql_log_bin
globally.
Incorrect use of
sql_log_bin
with a global
scope means any changes made in an already running session
are still being recorded to the
binary log and therefore replicated. Exercise extreme
caution using sql_log_bin
with a global scope as the above situation could cause
unexpected results including replication failure.
Command-Line Format | --sync-binlog=# |
---|---|
System Variable | sync_binlog |
Scope | Global |
Dynamic | Yes |
Type | Integer |
Default Value | 0 |
Minimum Value | 0 |
Maximum Value | 4294967295 |
Controls how often the MySQL server synchronizes the binary log to disk.
sync_binlog=0
: Disables
synchronization of the binary log to disk by the MySQL
server. Instead, the MySQL server relies on the
operating system to flush the binary log to disk from
time to time as it does for any other file. This setting
provides the best performance, but in the event of a
power failure or operating system crash, it is possible
that the server has committed transactions that have not
been synchronized to the binary log.
sync_binlog=1
: Enables
synchronization of the binary log to disk before
transactions are committed. This is the safest setting
but can have a negative impact on performance due to the
increased number of disk writes. In the event of a power
failure or operating system crash, transactions that are
missing from the binary log are only in a prepared
state. This permits the automatic recovery routine to
roll back the transactions, which guarantees that no
transaction is lost from the binary log.
sync_binlog=
,
where N
N
is a value other than
0 or 1: The binary log is synchronized to disk after
N
binary log commit groups have been
collected. In the event of a power failure or operating
system crash, it is possible that the server has
committed transactions that have not been flushed to the
binary log. This setting can have a negative impact on
performance due to the increased number of disk writes.
A higher value improves performance, but with an
increased risk of data loss.
For the greatest possible durability and consistency in a
replication setup that uses InnoDB
with
transactions, use these settings:
Many operating systems and some disk hardware fool the
flush-to-disk operation. They may tell
mysqld that the flush has taken place,
even though it has not. In this case, the durability of
transactions is not guaranteed even with the recommended
settings, and in the worst case, a power outage can
corrupt InnoDB
data. Using a
battery-backed disk cache in the SCSI disk controller or
in the disk itself speeds up file flushes, and makes the
operation safer. You can also try to disable the caching
of disk writes in hardware caches.