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Dynamic System Variables

Many server system variables are dynamic and can be set at runtime using SET GLOBAL or SET SESSION. You can also obtain their values using SELECT. See Section 5.1.5, “Using System Variables”.

The following table shows the full list of all dynamic system variables. The last column indicates for each variable whether GLOBAL or SESSION (or both) apply. The table also lists session options that can be set with the SET statement. Section 5.1.4, “Session System Variables”, discusses these options.

Variables that have a type of “string” take a string value. Variables that have a type of “numeric” take a numeric value. Variables that have a type of “boolean” can be set to 0, 1, ON or OFF. (If you set them on the command line or in an option file, use the numeric values.) Variables that are marked as “enumeration” normally should be set to one of the available values for the variable, but can also be set to the number that corresponds to the desired enumeration value. For enumerated system variables, the first enumeration value corresponds to 0. This differs from ENUM columns, for which the first enumeration value corresponds to 1.

Variable Name	Variable Type	Variable Scope
auto_increment_increment	numeric	GLOBAL | SESSION
auto_increment_offset	numeric	GLOBAL | SESSION
autocommit	boolean	SESSION
automatic_sp_privileges	boolean	GLOBAL
big_tables	boolean	SESSION
binlog_cache_size	numeric	GLOBAL
binlog_format	enumeration	GLOBAL | SESSION
bulk_insert_buffer_size	numeric	GLOBAL | SESSION
character_set_client	string	GLOBAL | SESSION
character_set_connection	string	GLOBAL | SESSION
character_set_database	string	GLOBAL | SESSION
character_set_filesystem	string	GLOBAL | SESSION
character_set_results	string	GLOBAL | SESSION
character_set_server	string	GLOBAL | SESSION
collation_connection	string	GLOBAL | SESSION
collation_database	string	GLOBAL | SESSION
collation_server	string	GLOBAL | SESSION
completion_type	numeric	GLOBAL | SESSION
concurrent_insert	boolean	GLOBAL
connect_timeout	numeric	GLOBAL
date_format	string	GLOBAL | SESSION
datetime_format	string	GLOBAL | SESSION
debug	string	GLOBAL | SESSION
default_week_format	numeric	GLOBAL | SESSION
delay_key_write	enumeration	GLOBAL
delayed_insert_limit	numeric	GLOBAL
delayed_insert_timeout	numeric	GLOBAL
delayed_queue_size	numeric	GLOBAL
div_precision_increment	numeric	GLOBAL | SESSION
engine_condition_pushdown	boolean	GLOBAL | SESSION
event_scheduler	enumeration	GLOBAL
expire_logs_days	numeric	GLOBAL
flush	boolean	GLOBAL
flush_time	numeric	GLOBAL
foreign_key_checks	boolean	SESSION
ft_boolean_syntax	string	GLOBAL
general_log	boolean	GLOBAL
general_log_file	filename	GLOBAL
group_concat_max_len	numeric	GLOBAL | SESSION
identity	numeric	SESSION
init_connect	string	GLOBAL
init_slave	string	GLOBAL
innodb_autoextend_increment	numeric	GLOBAL
innodb_commit_concurrency	numeric	GLOBAL
innodb_concurrency_tickets	numeric	GLOBAL
innodb_fast_shutdown	boolean	GLOBAL
innodb_flush_log_at_trx_commit	numeric	GLOBAL
innodb_max_dirty_pages_pct	numeric	GLOBAL
innodb_max_purge_lag	numeric	GLOBAL
innodb_stats_on_metadata	boolean	GLOBAL
innodb_support_xa	boolean	GLOBAL | SESSION
innodb_sync_spin_loops	numeric	GLOBAL
innodb_table_locks	boolean	GLOBAL | SESSION
innodb_thread_concurrency	numeric	GLOBAL
innodb_thread_sleep_delay	numeric	GLOBAL
innodb_use_legacy_cardinality_algorithm	boolean	GLOBAL
insert_id	numeric	SESSION
interactive_timeout	numeric	GLOBAL | SESSION
join_buffer_size	numeric	GLOBAL | SESSION
keep_files_on_create	boolean	GLOBAL | SESSION
key_buffer_size	numeric	GLOBAL
key_cache_age_threshold	numeric	GLOBAL
key_cache_block_size	numeric	GLOBAL
key_cache_division_limit	numeric	GLOBAL
last_insert_id	numeric	SESSION
lc_time_names	string	GLOBAL | SESSION
local_infile		GLOBAL
log	string	GLOBAL
log_bin_trust_function_creators	boolean	GLOBAL
log_bin_trust_routine_creators	boolean	GLOBAL
log_output	enumeration	GLOBAL
log_queries_not_using_indexes	boolean	GLOBAL
log_slow_queries	boolean	GLOBAL
log_warnings	numeric	GLOBAL | SESSION
long_query_time	numeric	GLOBAL | SESSION
low_priority_updates	boolean	GLOBAL | SESSION
max_allowed_packet	numeric	GLOBAL | SESSION
max_binlog_cache_size	numeric	GLOBAL
max_binlog_size	numeric	GLOBAL
max_connect_errors	numeric	GLOBAL
max_connections	numeric	GLOBAL
max_delayed_threads	numeric	GLOBAL | SESSION
max_error_count	numeric	GLOBAL | SESSION
max_heap_table_size	numeric	GLOBAL | SESSION
max_insert_delayed_threads	numeric	GLOBAL | SESSION
max_join_size	numeric	GLOBAL | SESSION
max_length_for_sort_data	numeric	GLOBAL | SESSION
max_prepared_stmt_count	numeric	GLOBAL
max_relay_log_size	numeric	GLOBAL
max_seeks_for_key	numeric	GLOBAL | SESSION
max_sort_length	numeric	GLOBAL | SESSION
max_sp_recursion_depth	numeric	GLOBAL | SESSION
max_tmp_tables	numeric	GLOBAL | SESSION
max_user_connections	numeric	GLOBAL | SESSION
max_write_lock_count	numeric	GLOBAL
min_examined_row_limit	numeric	GLOBAL | SESSION
multi_range_count	numeric	GLOBAL | SESSION
myisam_data_pointer_size	numeric	GLOBAL
myisam_max_sort_file_size	numeric	GLOBAL
myisam_repair_threads	numeric	GLOBAL | SESSION
myisam_sort_buffer_size	numeric	GLOBAL | SESSION
myisam_stats_method	enumeration	GLOBAL | SESSION
myisam_use_mmap	boolean	GLOBAL
ndb_autoincrement_prefetch_sz	numeric	GLOBAL | SESSION
ndb_cache_check_time	numeric	GLOBAL
ndb_extra_logging	numeric	GLOBAL
ndb_force_send	boolean	GLOBAL | SESSION
ndb_log_empty_epochs	boolean	GLOBAL
ndb_log_update_as_write	boolean	GLOBAL
ndb_log_updated_only	boolean	GLOBAL
ndb_optimization_delay	numeric	GLOBAL
ndb_table_no_logging	boolean	SESSION
ndb_table_temporary	boolean	SESSION
ndb_use_exact_count	boolean	GLOBAL | SESSION
net_buffer_length	numeric	GLOBAL | SESSION
net_read_timeout	numeric	GLOBAL | SESSION
net_retry_count	numeric	GLOBAL | SESSION
net_write_timeout	numeric	GLOBAL | SESSION
new	boolean	GLOBAL | SESSION
old_passwords	boolean	GLOBAL | SESSION
optimizer_prune_level	boolean	GLOBAL | SESSION
optimizer_search_depth	numeric	GLOBAL | SESSION
optimizer_switch	set	GLOBAL | SESSION
preload_buffer_size	numeric	GLOBAL | SESSION
profiling	boolean	SESSION
profiling_history_size	numeric	GLOBAL | SESSION
query_alloc_block_size	numeric	GLOBAL | SESSION
query_cache_limit	numeric	GLOBAL
query_cache_min_res_unit	numeric	GLOBAL
query_cache_size	numeric	GLOBAL
query_cache_type	enumeration	GLOBAL | SESSION
query_cache_wlock_invalidate	boolean	GLOBAL | SESSION
query_prealloc_size	numeric	GLOBAL | SESSION
rand_seed1	numeric	SESSION
rand_seed2	numeric	SESSION
range_alloc_block_size	numeric	GLOBAL | SESSION
read_buffer_size	numeric	GLOBAL | SESSION
read_only	numeric	GLOBAL
read_rnd_buffer_size	numeric	GLOBAL | SESSION
relay_log_purge	boolean	GLOBAL
rpl_recovery_rank	numeric	GLOBAL
safe_show_database	boolean	GLOBAL
secure_auth	boolean	GLOBAL
server_id	numeric	GLOBAL
slave_allow_batching	boolean	GLOBAL
slave_compressed_protocol	boolean	GLOBAL
slave_exec_mode	enumeration	GLOBAL
slave_net_timeout	numeric	GLOBAL
slave_transaction_retries	numeric	GLOBAL
slow_launch_time	numeric	GLOBAL
slow_query_log	boolean	GLOBAL
slow_query_log_file	filename	GLOBAL
sort_buffer_size	numeric	GLOBAL | SESSION
sql_auto_is_null	boolean	SESSION
sql_big_selects	boolean	SESSION
sql_big_tables	boolean	SESSION
sql_buffer_result	boolean	SESSION
sql_log_bin	boolean	SESSION
sql_log_off	boolean	SESSION
sql_log_update	boolean	SESSION
sql_low_priority_updates	boolean	GLOBAL | SESSION
sql_max_join_size	numeric	GLOBAL | SESSION
sql_mode	set	GLOBAL | SESSION
sql_notes	boolean	SESSION
sql_quote_show_create	boolean	SESSION
sql_safe_updates	boolean	SESSION
sql_select_limit	numeric	GLOBAL | SESSION
sql_slave_skip_counter	numeric	GLOBAL
sql_warnings	boolean	SESSION
storage_engine	enumeration	GLOBAL | SESSION
sync_binlog	numeric	GLOBAL
sync_frm	boolean	GLOBAL
table_cache	numeric	GLOBAL
table_definition_cache	numeric	GLOBAL
table_lock_wait_timeout	numeric	GLOBAL
table_open_cache	numeric	GLOBAL
table_type	enumeration	GLOBAL | SESSION
thread_cache_size	numeric	GLOBAL
time_format	string	GLOBAL | SESSION
time_zone	string	GLOBAL | SESSION
timed_mutexes	boolean	GLOBAL
timestamp	string	SESSION
tmp_table_size	numeric	GLOBAL | SESSION
transaction_alloc_block_size	numeric	GLOBAL | SESSION
transaction_allow_batching	boolean	SESSION
transaction_prealloc_size	numeric	GLOBAL | SESSION
tx_isolation	enumeration	GLOBAL | SESSION
unique_checks	boolean	SESSION
updatable_views_with_limit	boolean	GLOBAL | SESSION
wait_timeout	numeric	GLOBAL | SESSION