Chapter 10 Performance Schema System Variables
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Chapter 10 Performance Schema System Variables

The Performance Schema implements several system variables that provide configuration information:

mysql> SHOW VARIABLES LIKE 'perf%';
+--------------------------------------------------------+---------+
| Variable_name                                          | Value   |
+--------------------------------------------------------+---------+
| performance_schema                                     | ON      |
| performance_schema_accounts_size                       | 100     |
| performance_schema_digests_size                        | 200     |
| performance_schema_events_stages_history_long_size     | 10000   |
| performance_schema_events_stages_history_size          | 10      |
| performance_schema_events_statements_history_long_size | 10000   |
| performance_schema_events_statements_history_size      | 10      |
| performance_schema_events_waits_history_long_size      | 10000   |
| performance_schema_events_waits_history_size           | 10      |
| performance_schema_hosts_size                          | 100     |
| performance_schema_max_cond_classes                    | 80      |
| performance_schema_max_cond_instances                  | 1000    |
| performance_schema_max_file_classes                    | 50      |
| performance_schema_max_file_handles                    | 32768   |
| performance_schema_max_file_instances                  | 10000   |
| performance_schema_max_mutex_classes                   | 200     |
| performance_schema_max_mutex_instances                 | 1000000 |
| performance_schema_max_rwlock_classes                  | 30      |
| performance_schema_max_rwlock_instances                | 1000000 |
| performance_schema_max_socket_classes                  | 10      |
| performance_schema_max_socket_instances                | 1000    |
| performance_schema_max_stage_classes                   | 150     |
| performance_schema_max_statement_classes               | 165     |
| performance_schema_max_table_handles                   | 10000   |
| performance_schema_max_table_instances                 | 1000    |
| performance_schema_max_thread_classes                  | 50      |
| performance_schema_max_thread_instances                | 1000    |
| performance_schema_session_connect_attrs_size          | 512     |
| performance_schema_setup_actors_size                   | 100     |
| performance_schema_setup_objects_size                  | 100     |
| performance_schema_users_size                          | 100     |
+--------------------------------------------------------+---------+

Performance Schema system variables can be set at server startup on the command line or in option files, and many can be set at runtime. See Performance Schema Option and Variable Reference.

As of MySQL 5.6.6, the Performance Schema automatically sizes the values of several of its parameters at server startup if they are not set explicitly. For more information, see Section 3.2, “Performance Schema Startup Configuration”.

Performance Schema system variables have the following meanings:

performance_schema

Command-Line Format	`--performance_schema=#`
System Variable	Name	`performance_schema`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`boolean`
	Default	`OFF`
Permitted Values (>= 5.6.6)	Type	`boolean`
	Default	`ON`

The value of this variable is ON or OFF to indicate whether the Performance Schema is enabled. By default, the value is ON by default as of MySQL 5.6.6 and OFF before that. At server startup, you can specify this variable with no value or a value of ON or 1 to enable it, or with a value of OFF or 0 to disable it.

performance_schema_accounts_size

Introduced	5.6.3
Command-Line Format	`--performance_schema_accounts_size=#`
System Variable	Name	`performance_schema_accounts_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`10`
	Min Value	`0`
	Max Value	`1048576`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`
	Min Value	`-1 (autosized)`
	Max Value	`1048576`

The number of rows in the accounts table. If this variable is 0, the Performance Schema does not maintain connection statistics in the accounts table. This variable was added in MySQL 5.6.3.

performance_schema_digests_size

Introduced	5.6.5
Command-Line Format	`--performance_schema_digests_size=#`
System Variable	Name	`performance_schema_digests_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`-1 (autosized)`
	Min Value	`-1`
	Max Value	`1048576`

The maximum number of rows in the events_statements_summary_by_digest table. This variable was added in MySQL 5.6.5. If this maximum is exceeded such that a digest cannot be instrumented, the Performance Schema increments the Performance_schema_digest_lost status variable.

performance_schema_events_stages_history_long_size

Introduced	5.6.3
Command-Line Format	`--performance_schema_events_stages_history_long_size=#`
System Variable	Name	`performance_schema_events_stages_history_long_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`10000`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The number of rows in the events_stages_history_long table. This variable was added in MySQL 5.6.3.

performance_schema_events_stages_history_size

Introduced	5.6.3
Command-Line Format	`--performance_schema_events_stages_history_size=#`
System Variable	Name	`performance_schema_events_stages_history_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`10`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The number of rows per thread in the events_stages_history table. This variable was added in MySQL 5.6.3.

performance_schema_events_statements_history_long_size

Introduced	5.6.3
Command-Line Format	`--performance_schema_events_statements_history_long_size=#`
System Variable	Name	`performance_schema_events_statements_history_long_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`10000`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The number of rows in the events_statements_history_long table. This variable was added in MySQL 5.6.3.

performance_schema_events_statements_history_size

Introduced	5.6.3
Command-Line Format	`--performance_schema_events_statements_history_size=#`
System Variable	Name	`performance_schema_events_statements_history_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`10`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The number of rows per thread in the events_statements_history table. This variable was added in MySQL 5.6.3.

performance_schema_events_waits_history_long_size

Command-Line Format	`--performance_schema_events_waits_history_long_size=#`
System Variable	Name	`performance_schema_events_waits_history_long_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`10000`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The number of rows in the events_waits_history_long table.

performance_schema_events_waits_history_size

Command-Line Format	`--performance_schema_events_waits_history_size=#`
System Variable	Name	`performance_schema_events_waits_history_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`10`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The number of rows per thread in the events_waits_history table.

performance_schema_hosts_size

Introduced	5.6.3
Command-Line Format	`--performance_schema_hosts_size=#`
System Variable	Name	`performance_schema_hosts_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`10`
	Min Value	`0`
	Max Value	`1048576`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`
	Min Value	`-1 (autosized)`
	Max Value	`1048576`

The number of rows in the hosts table. If this variable is 0, the Performance Schema does not maintain connection statistics in the hosts table. This variable was added in MySQL 5.6.3.

performance_schema_max_cond_classes

Command-Line Format --performance_schema_max_cond_classes=#
System Variable Name performance_schema_max_cond_classes
Variable Scope Global
Dynamic Variable No
Permitted Values Type integer
Default 80

The maximum number of condition instruments.

performance_schema_max_cond_instances

Command-Line Format	`--performance_schema_max_cond_instances=#`
System Variable	Name	`performance_schema_max_cond_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`1000`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The maximum number of instrumented condition objects.

performance_schema_max_digest_length

Introduced	5.6.26
Command-Line Format	`--performance_schema_max_digest_length=#`
System Variable	Name	`performance_schema_max_digest_length`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`1024`
	Min Value	`0`
	Max Value	`1048576`

The maximum number of bytes available for computing statement digests (see Performance Schema Statement Digests). This variable is like max_digest_length, but applies to the Performance Schema only. For more information, see the description of that variable in Server System Variables

This variable was added in MySQL 5.6.26. max_digest_length. In MySQL 5.6.24 and 5.6.25, use max_digest_length instead. Before 5.6.24, the value cannot be changed.

performance_schema_max_file_classes

Command-Line Format --performance_schema_max_file_classes=#
System Variable Name performance_schema_max_file_classes
Variable Scope Global
Dynamic Variable No
Permitted Values Type integer
Default 50

The maximum number of file instruments.
performance_schema_max_file_handles

Command-Line Format --performance_schema_max_file_handles=#
System Variable Name performance_schema_max_file_handles
Variable Scope Global
Dynamic Variable No
Permitted Values Type integer
Default 32768

The maximum number of opened file objects.
The value of performance_schema_max_file_handles should be greater than the value of open_files_limit: open_files_limit affects the maximum number of open file handles the server can support and performance_schema_max_file_handles affects how many of these file handles can be instrumented.

performance_schema_max_file_instances

Command-Line Format	`--performance_schema_max_file_instances=#`
System Variable	Name	`performance_schema_max_file_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`10000`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The maximum number of instrumented file objects.

performance_schema_max_mutex_classes

Command-Line Format --performance_schema_max_mutex_classes=#
System Variable Name performance_schema_max_mutex_classes
Variable Scope Global
Dynamic Variable No
Permitted Values Type integer
Default 200

The maximum number of mutex instruments.

performance_schema_max_mutex_instances

Command-Line Format	`--performance_schema_max_mutex_instances=#`
System Variable	Name	`performance_schema_max_mutex_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`1000`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The maximum number of instrumented mutex objects.

performance_schema_max_rwlock_classes

Command-Line Format	`--performance_schema_max_rwlock_classes=#`
System Variable	Name	`performance_schema_max_rwlock_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (5.6.0)	Type	`integer`
	Default	`20`
Permitted Values (>= 5.6.1, <= 5.6.14)	Type	`integer`
	Default	`30`
Permitted Values (>= 5.6.15)	Type	`integer`
	Default	`40`

The maximum number of rwlock instruments.

performance_schema_max_rwlock_instances

Command-Line Format	`--performance_schema_max_rwlock_instances=#`
System Variable	Name	`performance_schema_max_rwlock_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`1000`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The maximum number of instrumented rwlock objects.

performance_schema_max_socket_classes

Introduced	5.6.3
Command-Line Format	`--performance_schema_max_socket_classes=#`
System Variable	Name	`performance_schema_max_socket_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`10`

The maximum number of socket instruments. This variable was added in MySQL 5.6.3.

performance_schema_max_socket_instances

Introduced	5.6.3
Command-Line Format	`--performance_schema_max_socket_instances=#`
System Variable	Name	`performance_schema_max_socket_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`1000`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The maximum number of instrumented socket objects. This variable was added in MySQL 5.6.3.

performance_schema_max_stage_classes

Introduced	5.6.3
Command-Line Format	`--performance_schema_max_stage_classes=#`
System Variable	Name	`performance_schema_max_stage_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`150`

The maximum number of stage instruments. This variable was added in MySQL 5.6.3.

performance_schema_max_statement_classes

Introduced	5.6.3
Command-Line Format	`--performance_schema_max_statement_classes=#`
System Variable	Name	`performance_schema_max_statement_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`-1 (autosized)`

The maximum number of statement instruments. The default value is calculated at server build time based on the number of commands in the client/server protocol and the number of SQL statement types supported by the server.

This variable should not be changed, unless to set it to 0 to disable all statement instrumentation and save all memory associated with it. Setting the variable to nonzero values other than the default has no benefit; in particular, values larger than the default cause more memory to be allocated then is needed.

This variable was added in MySQL 5.6.3.

performance_schema_max_table_handles

Command-Line Format	`--performance_schema_max_table_handles=#`
System Variable	Name	`performance_schema_max_table_handles`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`100000`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The maximum number of opened table objects.

performance_schema_max_table_instances

Command-Line Format	`--performance_schema_max_table_instances=#`
System Variable	Name	`performance_schema_max_table_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`50000`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The maximum number of instrumented table objects.

performance_schema_max_thread_classes

Command-Line Format --performance_schema_max_thread_classes=#
System Variable Name performance_schema_max_thread_classes
Variable Scope Global
Dynamic Variable No
Permitted Values Type integer
Default 50

The maximum number of thread instruments.

performance_schema_max_thread_instances

Command-Line Format	`--performance_schema_max_thread_instances=#`
System Variable	Name	`performance_schema_max_thread_instances`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`1000`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`

The maximum number of instrumented thread objects. The value controls the size of the threads table. If this maximum is exceeded such that a thread cannot be instrumented, the Performance Schema increments the Performance_schema_thread_instances_lost status variable.

The max_connections system variable affects how many threads are run in the server. performance_schema_max_thread_instances affects how many of these running threads can be instrumented. The default value of performance_schema_max_thread_instances is autosized based on the value of max_connections.

performance_schema_session_connect_attrs_size

Introduced	5.6.6
Command-Line Format	`--performance_schema_session_connect_attrs_size=#`
System Variable	Name	`performance_schema_session_connect_attrs_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`-1 (autosized)`
	Min Value	`-1`
	Max Value	`1048576`

The amount of preallocated memory per thread reserved to hold connection attribute key/value pairs. If the aggregate size of connection attribute data sent by a client is larger than this amount, the Performance Schema truncates the attribute data, increments the Performance_schema_session_connect_attrs_lost status variable, and writes a message to the error log indicating that truncation occurred if the log_warnings system variable value is greater than zero.

The default value of performance_schema_session_connect_attrs_size is autosized at server startup. This value may be small, so if truncation occurs (Performance_schema_session_connect_attrs_lost becomes nonzero), you may wish to set performance_schema_session_connect_attrs_size explicitly to a larger value.

Although the maximum permitted performance_schema_session_connect_attrs_size value is 1MB, the effective maximum is 64KB because the server imposes a limit of 64KB on the aggregate size of connection attribute data it will accept. If a client attempts to send more than 64KB of attribute data, the server rejects the connection. For more information, see Section 8.8, “Performance Schema Connection Attribute Tables”.

This variable was added in MySQL 5.6.7.

performance_schema_setup_actors_size

Introduced	5.6.1
Command-Line Format	`--performance_schema_setup_actors_size=#`
System Variable	Name	`performance_schema_setup_actors_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`100`

The number of rows in the setup_actors table.

performance_schema_setup_objects_size

Introduced	5.6.1
Command-Line Format	`--performance_schema_setup_objects_size=#`
System Variable	Name	`performance_schema_setup_objects_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`100`

The number of rows in the setup_objects table.

performance_schema_users_size

Introduced	5.6.3
Command-Line Format	`--performance_schema_users_size=#`
System Variable	Name	`performance_schema_users_size`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values (<= 5.6.5)	Type	`integer`
	Default	`10`
	Min Value	`0`
	Max Value	`1048576`
Permitted Values (>= 5.6.6)	Type	`integer`
	Default	`-1 (autosized)`
	Min Value	`-1 (autosized)`
	Max Value	`1048576`

The number of rows in the users table. If this variable is 0, the Performance Schema does not maintain connection statistics in the users table. This variable was added in MySQL 5.6.3.

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Command-Line Format	`--performance_schema_max_cond_classes=#`
System Variable	Name	`performance_schema_max_cond_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`80`

Command-Line Format	`--performance_schema_max_file_classes=#`
System Variable	Name	`performance_schema_max_file_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`50`

Command-Line Format	`--performance_schema_max_file_handles=#`
System Variable	Name	`performance_schema_max_file_handles`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`32768`

Command-Line Format	`--performance_schema_max_mutex_classes=#`
System Variable	Name	`performance_schema_max_mutex_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`200`

Command-Line Format	`--performance_schema_max_thread_classes=#`
System Variable	Name	`performance_schema_max_thread_classes`
	Variable Scope	Global
	Dynamic Variable	No
Permitted Values	Type	`integer`
	Default	`50`