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 5.2.4, “The Binary Log”. For additional information about using MySQL server options and system variables, see Section 5.1.3, “Server Command Options”, and Section 5.1.4, “Server System Variables”.
Startup options used with binary logging. The following list describes startup options for enabling and configuring the binary log. System variables used with binary logging are discussed later in this section.
| Command-Line Format | --binlog-row-event-max-size=# | ||
| Option-File Format | binlog-row-event-max-size | ||
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. The default is 1024. See Section 16.1.2, “Replication Formats”.
| Command-Line Format | --log-bin | ||
| Option-File Format | log-bin | ||
| Variable Name | log_bin | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | file name | ||
| Default | OFF | ||
Enable binary logging. The server logs all statements that change data to the binary log, which is used for backup and replication. See Section 5.2.4, “The Binary Log”.
The option value, if given, is the basename for the log
sequence. The server creates binary log files in sequence by
adding a numeric suffix to the basename. It is recommended
that you specify a basename (see Section C.5.8, “Known Issues in MySQL”, for
the reason). Otherwise, MySQL uses
as the basename.
host_name-bin
In MySQL 5.5.20 and later, when the server reads an entry from
the index file, it checks whether the entry contains a
relative path, and if it does, the relative part of the path
in replaced with the absolute path set using the
--log-bin option. An absolute path remains
unchanged; in such a case, the index must be edited manually
to enable the new path or paths to be used. Previous to MySQL
5.5.20, 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 basename. This is a known issue; see Bug #19614 for
more information.
| Command-Line Format | --log-bin-index=name | ||
| Option-File Format | log-bin-index | ||
| Permitted Values | |||
| Type | file name | ||
| Default | OFF | ||
The index file for binary log file names. See
Section 5.2.4, “The Binary Log”. If you omit the file name, and
if you did not specify one with
--log-bin, MySQL uses
as the file name.
host_name-bin.index
--log-bin-trust-function-creators[={0|1}]
| Command-Line Format | --log-bin-trust-function-creators | ||
| Option-File Format | log-bin-trust-function-creators | ||
| Option Sets Variable | Yes, log_bin_trust_function_creators | ||
| Variable Name | log_bin_trust_function_creators | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
This option sets the corresponding
log_bin_trust_function_creators
system variable. If no argument is given, the option sets the
variable to 1.
log_bin_trust_function_creators
affects how MySQL enforces restrictions on stored function and
trigger creation. See
Section 19.7, “Binary Logging of Stored Programs”.
--log-bin-use-v1-row-events[={0|1}]
| Version Introduced | 5.5.15-ndb-7.2.1 | ||
| Command-Line Format | --log-bin-use-v1-row-events[={0|1}] | ||
| Option-File Format | log-bin-use-v1-row-events | ||
| Option Sets Variable | Yes, log_bin_use_v1_row_events | ||
| Variable Name | log-bin-use-v1-row-events | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
Version 2 binary log row events are used by default beginning
with MySQL Cluster NDB 7.2.1; however, Version 2 events cannot
be read by previous MySQL Cluster releases. Setting
--log-bin-use-v1-row-events to 1 causes
mysqld to write the binary log using
Version 1 logging events, which is the only version of binary
log events used in previous releases, and thus produce binary
logs that can be read by older slaves.
The value used for this option can be obtained from the
read-only
log_bin_use_v1_row_events
system variable.
--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 option and
--ndb-log-transaction-id are
not compatible.
Version 2 binary log row events are also available in MySQL Cluster NDB 7.0.27 and MySQL Cluster NDB 7.1.6 and later MySQL Cluster NDB 7.0 and 7.1 releases. However, prior to MySQL Cluster NDB 7.2.1, Version 1 events are the default (and so the default value for this option is 1 in those versions). You should keep this mind when planning upgrades for setups using MySQL Cluster Replication.
--log-bin-use-v1-row-events is not supported
in mainline MySQL Server 5.5 releases.
For more information, see Section 17.6.11, “MySQL Cluster Replication Conflict Resolution”.
| Command-Line Format | --log-short-format | ||
| Option-File Format | log-short-format | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
Log less information to the binary log and slow query log, if they have been activated.
Statement selection options. The options in the following list affect which statements are written to the binary log, and thus sent by a replication master server to its slaves. There are also options for slave servers that control which statements received from the master should be executed or ignored. For details, see Section 16.1.3.3, “Replication Slave Options and Variables”.
| Command-Line Format | --binlog-do-db=name | ||
| Option-File Format | binlog-do-db | ||
| Permitted Values | |||
| 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 will be treated as the name of a single database if you supply a comma-separated list.
An example of what does not work as you might expect when
using statement-based logging: If the server is started with
--binlog-do-db=sales and you
issue the following statements, the
UPDATE statement is
not logged:
USE prices; UPDATE sales.january SET amount=amount+1000;
The main reason for this “just check the default
database” behavior is that it is difficult from the
statement alone to know whether it should be replicated (for
example, if you are using multiple-table
DELETE statements or
multiple-table UPDATE
statements that act across multiple databases). It is also
faster to check only the default database rather than all
databases if there is no need.
Another case which may not be self-evident occurs when a given
database is replicated even though it was not specified when
setting the option. If the server is started with
--binlog-do-db=sales, the following
UPDATE statement is logged even
though prices was not included when setting
--binlog-do-db:
USE sales; UPDATE prices.discounts SET percentage = percentage + 10;
Because sales is the default database when
the UPDATE statement is issued,
the UPDATE is logged.
Row-based logging.
Logging is restricted to database
db_name. Only changes to tables
belonging to db_name are logged;
the default database has no effect on this. Suppose that the
server is started with
--binlog-do-db=sales and
row-based logging is in effect, and then the following
statements are executed:
USE prices; UPDATE sales.february SET amount=amount+100;
The changes to the february table in the
sales database are logged in accordance
with the UPDATE statement; this
occurs whether or not the USE
statement was issued. However, when using the row-based
logging format and
--binlog-do-db=sales, changes
made by the following UPDATE
are not logged:
USE prices; UPDATE prices.march SET amount=amount-25;
Even if the USE prices statement were
changed to USE sales, the
UPDATE statement's effects
would still not be written to the binary log.
Another important difference in
--binlog-do-db handling for
statement-based logging as opposed to the row-based logging
occurs with regard to statements that refer to multiple
databases. Suppose that the server is started with
--binlog-do-db=db1, and the
following statements are executed:
USE db1; UPDATE db1.table1 SET col1 = 10, db2.table2 SET col2 = 20;
If you are using statement-based logging, the updates to both
tables are written to the binary log. However, when using the
row-based format, only the changes to
table1 are logged;
table2 is in a different database, so it is
not changed by the UPDATE. Now
suppose that, instead of the USE db1
statement, a USE db4 statement had been
used:
USE db4; UPDATE db1.table1 SET col1 = 10, db2.table2 SET col2 = 20;
In this case, the UPDATE
statement is not written to the binary log when using
statement-based logging. However, when using row-based
logging, the change to table1 is logged,
but not that to table2—in other
words, only changes to tables in the database named by
--binlog-do-db are logged, and
the choice of default database has no effect on this behavior.
| Command-Line Format | --binlog-ignore-db=name | ||
| Option-File Format | binlog-ignore-db | ||
| Permitted Values | |||
| 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 5.5.32, 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 5.5.32 and later, when
there is no default database, no
--binlog-ignore-db options are applied, and
such statements are always logged. (Bug #11829838, Bug #60188)
Row-based format.
Tells the server not to log updates to any tables in the
database db_name. The current
database has no effect.
When using statement-based logging, the following example does
not work as you might expect. Suppose that the server is
started with
--binlog-ignore-db=sales and
you issue the following statements:
USE prices; UPDATE sales.january SET amount=amount+1000;
The UPDATE statement
is logged in such a case because
--binlog-ignore-db applies only
to the default database (determined by the
USE statement). Because the
sales database was specified explicitly in
the statement, the statement has not been filtered. However,
when using row-based logging, the
UPDATE statement's effects
are not written to the binary log, which
means that no changes to the sales.january
table are logged; in this instance,
--binlog-ignore-db=sales causes
all changes made to tables in the
master's copy of the sales database to
be ignored for purposes of binary logging.
To specify more than one database to ignore, use this option multiple times, once for each database. Because database names can contain commas, the list will be treated as the name of a single database if you supply a comma-separated list.
You should not use this option if you are using cross-database updates and you do not want these updates to be logged.
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=# | ||
| Option-File Format | max-binlog-dump-events | ||
| Permitted Values | |||
| Type | numeric | ||
| Default | 0 | ||
This option is used internally by the MySQL test suite for replication testing and debugging.
| Command-Line Format | --sporadic-binlog-dump-fail | ||
| Option-File Format | sporadic-binlog-dump-fail | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
This option is used internally by the MySQL test suite for replication testing and debugging.
System variables used with the binary log.
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.
| Variable Name | log_bin | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
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.
| Command-Line Format | --log-slave-updates | ||
| Option-File Format | log_slave_updates | ||
| Option Sets Variable | Yes, log_slave_updates | ||
| Variable Name | log_slave_updates | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | FALSE | ||
Whether updates received by a slave server from a master server should be logged to the slave's own binary log. Binary logging must be enabled on the slave for this variable to have any effect. See Section 16.1.3, “Replication and Binary Logging Options and Variables”.
| Command-Line Format | --binlog_cache_size=# | ||
| Option-File Format | binlog_cache_size | ||
| Option Sets Variable | Yes, binlog_cache_size | ||
| Variable Name | binlog_cache_size | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Platform Bit Size | 32 | ||
| Type | numeric | ||
| Default | 32768 | ||
| Range | 4096 .. 4294967295 | ||
| Permitted Values | |||
| Platform Bit Size | 64 | ||
| Type | numeric | ||
| Default | 32768 | ||
| Range | 4096 .. 18446744073709547520 | ||
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 5.2.4, “The Binary Log”.
In MySQL 5.5.3, a separate binary log cache (the binary log
statement cache) was introduced for nontransactional
statements and in MySQL 5.5.3 through 5.5.8, this variable
sets.the size for both caches. This means that, in these MySQL
versions, the total memory used for these caches is double the
value set for binlog_cache_size.
Beginning with MySQL 5.5.9,
binlog_cache_size sets the size for the
transaction cache only, and the size of the statement cache is
governed by the
binlog_stmt_cache_size system
variable.
binlog_direct_non_transactional_updates
| Version Introduced | 5.5.2 | ||
| Command-Line Format | --binlog_direct_non_transactional_updates[=value] | ||
| Option-File Format | binlog_direct_non_transactional_updates | ||
| Option Sets Variable | Yes, binlog_direct_non_transactional_updates | ||
| Variable Name | binlog_direct_non_transactional_updates | ||
| Variable Scope | Global, Session | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | boolean | ||
| Default | OFF | ||
Due to concurrency issues, a slave can become inconsistent when a transaction contains updates to both transactional and nontransactional tables. MySQL tries to preserve causality among these statements by writing nontransactional statements to the transaction cache, which is flushed upon commit. However, problems arise when modifications done to nontransactional tables on behalf of a transaction become immediately visible to other connections because these changes may not be written immediately into the binary log.
Beginning with MySQL 5.5.2, 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
.
Otherwise, such statements are likely to cause the slave to
diverge from the master.
myisam_table SELECT * FROM
innodb_table
Beginning with MySQL 5.5.5, this variable has no effect when
the binary log format is ROW or
MIXED. (Bug #51291)
| Command-Line Format | --binlog-format=format | ||
| Option-File Format | binlog-format=format | ||
| Option Sets Variable | Yes, binlog_format | ||
| Variable Name | binlog_format | ||
| Variable Scope | Global, Session | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | enumeration | ||
| Default | STATEMENT | ||
| Valid Values | ROW | ||
STATEMENT | |||
MIXED | |||
This variable sets the binary logging format, and can be any
one of STATEMENT, ROW,
or MIXED. See
Section 16.1.2, “Replication Formats”.
binlog_format is set by the
--binlog-format option at
startup, or by the
binlog_format system variable
at runtime.
While you can change the logging format at runtime, it is
not recommended that you change it
while replication is ongoing. This is due in part to the
fact that slaves do not honor the master's
binlog_format setting; a
given MySQL Server can change only its own logging format.
In MySQL 5.5, the default format is
STATEMENT.
Exception.
In MySQL Cluster NDB 7.2.1 through MySQL Cluster NDB 7.2.12,
the default for this variable is
STATEMENT. In MySQL Cluster NDB 7.2.13
and later, when the NDB storage
engine is enabled, the default is MIXED.
(Bug #16417224) See also
Section 17.6.6, “Starting MySQL Cluster Replication (Single Replication Channel)”, and
Section 17.6.7, “Using Two Replication Channels for MySQL Cluster Replication”.
You must have the SUPER
privilege to set either the global or session
binlog_format value.
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. See Section 13.7.4, “SET Syntax”,
for more information.
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. An exception to this rule is that
MIXED always uses statement-based
replication for stored functions and triggers.
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.
Beginning with MySQL 5.5.3, within a transaction. (Bug #47863)
Trying to switch the format in those cases results in an error.
Prior to MySQL Cluster NDB 7.2.1, it was also not possible
to change the binary logging format at runtime when the
NDBCLUSTER storage engine was
enabled. In MySQL Cluster NDB 7.2.1 and later, this
restriction is removed.
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.
| Version Introduced | 5.5.9 | ||
| Command-Line Format | --binlog_stmt_cache_size=# | ||
| Option-File Format | binlog_stmt_cache_size | ||
| Option Sets Variable | Yes, binlog_stmt_cache_size | ||
| Variable Name | binlog_stmt_cache_size | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Platform Bit Size | 32 | ||
| Type | numeric | ||
| Default | 32768 | ||
| Range | 4096 .. 4294967295 | ||
| Permitted Values | |||
| Platform Bit Size | 64 | ||
| Type | numeric | ||
| Default | 32768 | ||
| Range | 4096 .. 18446744073709547520 | ||
Beginning with MySQL 5.5.9, this variable determines the size
of the cache for the binary log to hold nontransactional
statements issued during a transaction. In MySQL 5.5.3 and
later, 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 more
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 5.2.4, “The Binary Log”.
In MySQL 5.5.3 through 5.5.8, the size for both caches is set
using binlog_cache_size. This
means that, in these MySQL versions, the total memory used for
these caches is double the value set for
binlog_cache_size. Beginning
with MySQL 5.5.9,
binlog_cache_size sets the
size for the transaction cache only.
| Version Introduced | 5.5.15-ndb-7.2.1 | ||
| Command-Line Format | --log-bin-use-v1-row-events[={0|1}] | ||
| Option-File Format | log_bin_use_v1_row_events | ||
| Option Sets Variable | Yes, log_bin_use_v1_row_events | ||
| Variable Name | log_bin_use_v1_row_events | ||
| Variable Scope | Global | ||
| Dynamic Variable | No | ||
Shows whether Version 2 binary logging, available beginning with MySQL Cluster NDB 7.2.1, is in use. A value of 1 shows that the server is writing the binary log using Version 1 logging events (the only version of binary log events used in previous releases), and thus producing a binary log that can be read by older slaves. 0 indicates that Version 2 binary log events are in use.
This variable is read-only. To switch between Version 1 and
Version 2 binary event binary logging, it is necessary to
restart mysqld with the
--log-bin-use-v1-row-events
option.
Other than when performing upgrades of MySQL Cluster
Replication, --log-bin-use-v1-events is
chiefly of interest when setting up replication conflict
detection and resolution using
NDB$EPOCH_TRANS(), which requires Version 2
binary row event logging. Thus, this option and
--ndb-log-transaction-id are
not compatible.
MySQL Cluster NDB 7.2.1 and later use Version 2 binary log row events by default (and so the default value for this variable changes to 0 in those versions). You should keep this mind when planning upgrades for setups using MySQL Cluster Replication.
This variable is not supported in mainline MySQL Server 5.5.
For more information, see Section 17.6.11, “MySQL Cluster Replication Conflict Resolution”.
| Command-Line Format | --max_binlog_cache_size=# | ||
| Option-File Format | max_binlog_cache_size | ||
| Option Sets Variable | Yes, max_binlog_cache_size | ||
| Variable Name | max_binlog_cache_size | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | numeric | ||
| Default | 18446744073709547520 | ||
| Range | 4096 .. 18446744073709547520 | ||
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.
Prior to MySQL 5.5.28, 64-bit Windows platforms truncated the stored value for this variable to 4G, even when it was set to a greater value (Bug #13961678).
In MySQL 5.5.3, a separate binary log cache (the binary log
statement cache) was introduced for nontransactional
statements and in MySQL 5.5.3 through 5.5.8, this variable
sets.the upper limit for both caches. This means that, in
these MySQL versions, the effective maximum for these caches
is double the value set for
max_binlog_cache_size.
Beginning with MySQL 5.5.9,
max_binlog_cache_size sets the size for the
transaction cache only, and the upper limit for the statement
cache is governed by the
max_binlog_stmt_cache_size
system variable.
Also beginning with MySQL 5.5.9, the session visibility of the
max_binlog_cache_size system
variable matches that of the
binlog_cache_size system
variable: In MySQL 5.5.8 and earlier releases, a change in
max_binlog_cache_size took
immediate effect; in MySQL 5.5.9 and later, a change in
max_binlog_cache_size takes
effect only for new sessions that started after the value is
changed.
| Command-Line Format | --max_binlog_size=# | ||
| Option-File Format | max_binlog_size | ||
| Option Sets Variable | Yes, max_binlog_size | ||
| Variable Name | max_binlog_size | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | numeric | ||
| Default | 1073741824 | ||
| Range | 4096 .. 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.
| Version Introduced | 5.5.9 | ||
| Command-Line Format | --max_binlog_stmt_cache_size=# | ||
| Option-File Format | max_binlog_stmt_cache_size | ||
| Option Sets Variable | Yes, max_binlog_stmt_cache_size | ||
| Variable Name | max_binlog_stmt_cache_size | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Type | numeric | ||
| Default | 18446744073709547520 | ||
| Range | 4096 .. 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.
Prior to MySQL 5.5.28, 64-bit Windows platforms truncated the stored value for this variable to 4G, even when it was set to a greater value (Bug #13961678).
In MySQL 5.5.3, a separate binary log cache (the binary log
statement cache) was introduced for nontransactional
statements and in MySQL 5.5.3 through 5.5.8, this variable
sets.the upper limit for both caches. This means that, in
these MySQL versions, the effective maximum for these caches
is double the value set for
max_binlog_cache_size.
Beginning with MySQL 5.5.9,
max_binlog_stmt_cache_size sets the size
for the statement cache only, and the upper limit for the
transaction cache is governed exclusively by the
max_binlog_cache_size system
variable.
| Command-Line Format | --sync-binlog=# | ||
| Option-File Format | sync_binlog | ||
| Option Sets Variable | Yes, sync_binlog | ||
| Variable Name | sync_binlog | ||
| Variable Scope | Global | ||
| Dynamic Variable | Yes | ||
| Permitted Values | |||
| Platform Bit Size | 32 | ||
| Type | numeric | ||
| Default | 0 | ||
| Range | 0 .. 4294967295 | ||
| Permitted Values | |||
| Platform Bit Size | 64 | ||
| Type | numeric | ||
| Default | 0 | ||
| Range | 0 .. 18446744073709547520 | ||
If the value of this variable is greater than 0, the MySQL
server synchronizes its binary log to disk (using
fdatasync()) after every
sync_binlog writes to the
binary log. There is one write to the binary log per statement
if autocommit is enabled, and one write per transaction
otherwise. The default value of
sync_binlog is 0, which does
no synchronizing to disk—in this case, the server relies
on the operating system to flush the binary log's
contents from to time as for any other file. A value of 1 is
the safest choice because in the event of a crash you lose at
most one statement or transaction from the binary log.
However, it is also the slowest choice (unless the disk has a
battery-backed cache, which makes synchronization very fast).

User Comments
Add your own comment.