5.1.4. Server System Variables

The MySQL server maintains many system variables that indicate how it is configured. Each system variable has a default value. System variables can be set at server startup using options on the command line or in an option file. Most of them can be changed dynamically while the server is running by means of the SET statement, which enables you to modify operation of the server without having to stop and restart it. You can refer to system variable values in expressions.

There are several ways to see the names and values of system variables:

This section provides a description of each system variable. Variables with no version indicated are present in all MySQL 5.7 releases. For historical information concerning their implementation, please see http://dev.mysql.com/doc/refman/5.0/en/, and http://dev.mysql.com/doc/refman/4.1/en/.

The following table lists all available system variables.

Table 5.2. System Variable Summary

Name Cmd-Line Option file System Var Var Scope Dynamic
auto_increment_increment Yes Both Yes
auto_increment_offset Yes Both Yes
autocommit Yes Yes Yes Both Yes
automatic_sp_privileges Yes Global Yes
back_log Yes Global No
basedir Yes Yes Yes Global No
bind-address Yes Yes No
- Variable: bind_address Yes Global No
binlog_cache_size Yes Yes Yes Global Yes
binlog_checksum Yes Global Yes
binlog_direct_non_transactional_updates Yes Yes Yes Both Yes
binlog-format Yes Yes Yes
- Variable: binlog_format Yes Both Yes
binlog_max_flush_queue_time Yes Global Yes
binlog_order_commits Yes Global Yes
binlog_row_image Yes Yes Yes Both Yes
binlog_rows_query_log_events Yes Both Yes
binlog_stmt_cache_size Yes Yes Yes Global Yes
bulk_insert_buffer_size Yes Yes Yes Both Yes
character_set_client Yes Both Yes
character_set_connection Yes Both Yes
character_set_database[a] Yes Both Yes
character-set-filesystem Yes Yes Yes
- Variable: character_set_filesystem Yes Both Yes
character_set_results Yes Both Yes
character-set-server Yes Yes Yes
- Variable: character_set_server Yes Both Yes
character_set_system Yes Global No
character-sets-dir Yes Yes No
- Variable: character_sets_dir Yes Global No
collation_connection Yes Both Yes
collation_database[b] Yes Both Yes
collation-server Yes Yes Yes
- Variable: collation_server Yes Both Yes
completion_type Yes Yes Yes Both Yes
concurrent_insert Yes Yes Yes Global Yes
connect_timeout Yes Yes Yes Global Yes
core_file Yes Global No
daemon_memcached_enable_binlog Yes Yes Yes Global No
daemon_memcached_engine_lib_name Yes Yes Yes Global No
daemon_memcached_engine_lib_path Yes Yes Yes Global No
daemon_memcached_option Yes Yes Yes Global No
daemon_memcached_r_batch_size Yes Yes Yes Global No
daemon_memcached_w_batch_size Yes Yes Yes Global No
datadir Yes Yes Yes Global No
date_format Yes Global No
datetime_format Yes Global No
debug Yes Yes Yes Both Yes
debug_sync Yes Session Yes
default-storage-engine Yes Yes Yes
- Variable: default_storage_engine Yes Both Yes
default_tmp_storage_engine Yes Yes Yes Both Yes
default_week_format Yes Yes Yes Both Yes
delay-key-write Yes Yes Yes
- Variable: delay_key_write Yes Global Yes
delayed_insert_limit Yes Yes Yes Global Yes
delayed_insert_timeout Yes Yes Yes Global Yes
delayed_queue_size Yes Yes Yes Global Yes
disconnect_on_expired_passwords Yes Yes Yes Session No
div_precision_increment Yes Yes Yes Both Yes
end_markers_in_json Yes Both Yes
enforce_gtid_consistency Yes Yes Yes Global No
enforce-gtid-consistency Yes Yes Yes Global No
eq_range_index_dive_limit Yes Both Yes
error_count Yes Session No
event-scheduler Yes Yes Yes
- Variable: event_scheduler Yes Global Yes
expire_logs_days Yes Yes Yes Global Yes
explicit_defaults_for_timestamp Yes Yes Yes Session No
external_user Yes Session No
flush Yes Yes Yes Global Yes
flush_time Yes Yes Yes Global Yes
foreign_key_checks Yes Both Yes
ft_boolean_syntax Yes Yes Yes Global Yes
ft_max_word_len Yes Yes Yes Global No
ft_min_word_len Yes Yes Yes Global No
ft_query_expansion_limit Yes Yes Yes Global No
ft_stopword_file Yes Yes Yes Global No
general-log Yes Yes Yes
- Variable: general_log Yes Global Yes
general_log_file Yes Yes Yes Global Yes
group_concat_max_len Yes Yes Yes Both Yes
gtid_executed Yes Both No
gtid_mode Yes Global No
gtid-mode Yes Yes No
- Variable: gtid_mode Yes Global No
gtid_next Yes Session Yes
gtid_owned Yes Both No
gtid_purged Yes Global Yes
have_compress Yes Global No
have_crypt Yes Global No
have_dynamic_loading Yes Global No
have_geometry Yes Global No
have_openssl Yes Global No
have_profiling Yes Global No
have_query_cache Yes Global No
have_rtree_keys Yes Global No
have_ssl Yes Global No
have_symlink Yes Global No
host_cache_size Yes Global Yes
hostname Yes Global No
identity Yes Session Yes
ignore-builtin-innodb Yes Yes No
- Variable: ignore_builtin_innodb Yes Global No
ignore_db_dirs Yes Global No
init_connect Yes Yes Yes Global Yes
init-file Yes Yes No
- Variable: init_file Yes Global No
init_slave Yes Yes Yes Global Yes
innodb_adaptive_flushing Yes Yes Yes Global Yes
innodb_adaptive_flushing_lwm Yes Yes Yes Global Yes
innodb_adaptive_hash_index Yes Yes Yes Global Yes
innodb_adaptive_max_sleep_delay Yes Yes Yes Global Yes
innodb_additional_mem_pool_size Yes Yes Yes Global No
innodb_api_bk_commit_interval Yes Yes Yes Global Yes
innodb_api_disable_rowlock Yes Yes Yes Global No
innodb_api_enable_binlog Yes Yes Yes Global No
innodb_api_enable_mdl Yes Yes Yes Global No
innodb_api_trx_level Yes Yes Yes Global Yes
innodb_autoextend_increment Yes Yes Yes Global Yes
innodb_autoinc_lock_mode Yes Yes Yes Global No
innodb_buffer_pool_dump_at_shutdown Yes Yes Yes Global Yes
innodb_buffer_pool_dump_now Yes Yes Yes Global Yes
innodb_buffer_pool_filename Yes Yes Yes Global Yes
innodb_buffer_pool_instances Yes Yes Yes Global No
innodb_buffer_pool_load_abort Yes Yes Yes Global Yes
innodb_buffer_pool_load_at_startup Yes Yes Yes Global No
innodb_buffer_pool_load_now Yes Yes Yes Global Yes
innodb_buffer_pool_size Yes Yes Yes Global No
innodb_change_buffer_max_size Yes Yes Yes Global Yes
innodb_change_buffering Yes Yes Yes Global Yes
innodb_checksum_algorithm Yes Yes Yes Global Yes
innodb_checksums Yes Yes Yes Global No
innodb_cmp_per_index_enabled Yes Yes Yes Global Yes
innodb_commit_concurrency Yes Yes Yes Global Yes
innodb_compression_failure_threshold_pct Yes Yes Yes Global Yes
innodb_compression_level Yes Yes Yes Global Yes
innodb_compression_pad_pct_max Yes Yes Yes Global Yes
innodb_concurrency_tickets Yes Yes Yes Global Yes
innodb_data_file_path Yes Yes Yes Global No
innodb_data_home_dir Yes Yes Yes Global No
innodb_disable_sort_file_cache Yes Yes Yes Global Yes
innodb_doublewrite Yes Yes Yes Global No
innodb_fast_shutdown Yes Yes Yes Global Yes
innodb_file_format Yes Yes Yes Global Yes
innodb_file_format_check Yes Yes Yes Global No
innodb_file_format_max Yes Yes Yes Global Yes
innodb_file_per_table Yes Yes Yes Global Yes
innodb_flush_log_at_timeout Yes Global Yes
innodb_flush_log_at_trx_commit Yes Yes Yes Global Yes
innodb_flush_method Yes Yes Yes Global No
innodb_flush_neighbors Yes Yes Yes Global Yes
innodb_flushing_avg_loops Yes Yes Yes Global Yes
innodb_force_load_corrupted Yes Yes Yes Global No
innodb_force_recovery Yes Yes Yes Global No
innodb_ft_aux_table Yes Yes Yes Global Yes
innodb_ft_cache_size Yes Yes Yes Global No
innodb_ft_enable_diag_print Yes Yes Yes Global Yes
innodb_ft_enable_stopword Yes Yes Yes Global Yes
innodb_ft_max_token_size Yes Yes Yes Global No
innodb_ft_min_token_size Yes Yes Yes Global No
innodb_ft_num_word_optimize Yes Yes Yes Global Yes
innodb_ft_server_stopword_table Yes Yes Yes Global Yes
innodb_ft_sort_pll_degree Yes Yes Yes Global No
innodb_ft_user_stopword_table Yes Yes Yes Both Yes
innodb_io_capacity Yes Yes Yes Global Yes
innodb_io_capacity_max Yes Yes Yes Global Yes
innodb_large_prefix Yes Yes Yes Global Yes
innodb_lock_wait_timeout Yes Yes Yes Both Yes
innodb_locks_unsafe_for_binlog Yes Yes Yes Global No
innodb_log_buffer_size Yes Yes Yes Global No
innodb_log_compressed_pages Yes Yes Yes Global Yes
innodb_log_file_size Yes Yes Yes Global No
innodb_log_files_in_group Yes Yes Yes Global No
innodb_log_group_home_dir Yes Yes Yes Global No
innodb_lru_scan_depth Yes Yes Yes Global Yes
innodb_max_dirty_pages_pct Yes Yes Yes Global Yes
innodb_max_dirty_pages_pct_lwm Yes Yes Yes Global Yes
innodb_max_purge_lag Yes Yes Yes Global Yes
innodb_max_purge_lag_delay Yes Yes Yes Global Yes
innodb_monitor_disable Yes Yes Yes Global Yes
innodb_monitor_enable Yes Yes Yes Global Yes
innodb_monitor_reset Yes Yes Yes Global Yes
innodb_monitor_reset_all Yes Yes Yes Global Yes
innodb_old_blocks_pct Yes Yes Yes Global Yes
innodb_old_blocks_time Yes Yes Yes Global Yes
innodb_online_alter_log_max_size Yes Yes Yes Global Yes
innodb_open_files Yes Yes Yes Global No
innodb_optimize_fulltext_only Yes Yes Yes Global Yes
innodb_page_size Yes Yes Yes Global No
innodb_print_all_deadlocks Yes Yes Yes Global Yes
innodb_purge_batch_size Yes Yes Yes Global Yes
innodb_purge_threads Yes Yes Yes Global No
innodb_random_read_ahead Yes Yes Yes Global Yes
innodb_read_ahead_threshold Yes Yes Yes Global Yes
innodb_read_io_threads Yes Yes Yes Global No
innodb_read_only Yes Yes Yes Global No
innodb_replication_delay Yes Yes Yes Global Yes
innodb_rollback_on_timeout Yes Yes Yes Global No
innodb_rollback_segments Yes Yes Yes Global Yes
innodb_sort_buffer_size Yes Yes Yes Global No
innodb_spin_wait_delay Yes Yes Yes Global Yes
innodb_stats_auto_recalc Yes Yes Yes Global Yes
innodb_stats_method Yes Yes Yes Global Yes
innodb_stats_on_metadata Yes Yes Yes Global Yes
innodb_stats_persistent Yes Yes Yes Global Yes
innodb_stats_persistent_sample_pages Yes Yes Yes Global Yes
innodb_stats_sample_pages Yes Yes Yes Global Yes
innodb_stats_transient_sample_pages Yes Yes Yes Global Yes
innodb_strict_mode Yes Yes Yes Both Yes
innodb_support_xa Yes Yes Yes Both Yes
innodb_sync_array_size Yes Yes Yes Global No
innodb_sync_spin_loops Yes Yes Yes Global Yes
innodb_table_locks Yes Yes Yes Both Yes
innodb_temp_data_file_path Yes Yes Yes Global No
innodb_thread_concurrency Yes Yes Yes Global Yes
innodb_thread_sleep_delay Yes Yes Yes Global Yes
innodb_undo_directory Yes Yes Yes Global No
innodb_undo_logs Yes Yes Yes Global Yes
innodb_undo_tablespaces Yes Yes Yes Global No
innodb_use_native_aio Yes Yes Yes Global No
innodb_use_sys_malloc Yes Yes Yes Global No
innodb_version Yes Global No
innodb_write_io_threads Yes Yes Yes Global No
insert_id Yes Session Yes
interactive_timeout Yes Yes Yes Both Yes
join_buffer_size Yes Yes Yes Both Yes
keep_files_on_create Yes Yes Yes Both Yes
key_buffer_size Yes Yes Yes Global Yes
key_cache_age_threshold Yes Yes Yes Global Yes
key_cache_block_size Yes Yes Yes Global Yes
key_cache_division_limit Yes Yes Yes Global Yes
language Yes Yes Yes Global No
large_files_support Yes Global No
large_page_size Yes Global No
large-pages Yes Yes No
- Variable: large_pages Yes Global No
last_insert_id Yes Session Yes
lc-messages Yes Yes Yes
- Variable: lc_messages Yes Both Yes
lc-messages-dir Yes Yes No
- Variable: lc_messages_dir Yes Global No
lc_time_names Yes Both Yes
license Yes Global No
local_infile Yes Global Yes
lock_wait_timeout Yes Yes Yes Both Yes
locked_in_memory Yes Global No
log_bin Yes Global No
log-bin Yes Yes Yes Global No
log_bin_basename Yes Global No
log_bin_use_v1_row_events Yes Yes Yes Global No
log-bin-use-v1-row-events Yes Yes No
- Variable: log_bin_use_v1_row_events Yes Global No
log-error Yes Yes No
- Variable: log_error Yes Global No
log-output Yes Yes Yes
- Variable: log_output Yes Global Yes
log-queries-not-using-indexes Yes Yes Yes
- Variable: log_queries_not_using_indexes Yes Global Yes
log-slave-updates Yes Yes No
- Variable: log_slave_updates Yes Global No
log_slave_updates Yes Yes Yes Global No
log_slow_admin_statements Yes Global Yes
log_slow_slave_statements Yes Global Yes
log_throttle_queries_not_using_indexes Yes Global Yes
log-warnings Yes Yes Yes
- Variable: log_warnings Yes Global Yes
long_query_time Yes Yes Yes Both Yes
low-priority-updates Yes Yes Yes
- Variable: low_priority_updates Yes Both Yes
lower_case_file_system Yes Yes Yes Global No
lower_case_table_names Yes Yes Yes Global No
master_info_repository Yes Global Yes
master_verify_checksum Yes Global Yes
max_allowed_packet Yes Yes Yes Global Yes
max_binlog_cache_size Yes Yes Yes Global Yes
max_binlog_size Yes Yes Yes Global Yes
max_binlog_stmt_cache_size Yes Yes Yes Global Yes
max_connect_errors Yes Yes Yes Global Yes
max_connections Yes Yes Yes Global Yes
max_delayed_threads Yes Yes Yes Both Yes
max_error_count Yes Yes Yes Both Yes
max_heap_table_size Yes Yes Yes Both Yes
max_insert_delayed_threads Yes Both Yes
max_join_size Yes Yes Yes Both Yes
max_length_for_sort_data Yes Yes Yes Both Yes
max_prepared_stmt_count Yes Yes Yes Global Yes
max_relay_log_size Yes Yes Yes Global Yes
max_seeks_for_key Yes Yes Yes Both Yes
max_sort_length Yes Yes Yes Both Yes
max_sp_recursion_depth Yes Yes Yes Both Yes
max_user_connections Yes Yes Yes Both Yes
max_write_lock_count Yes Yes Yes Global Yes
memlock Yes Yes Yes Global No
metadata_locks_cache_size Yes Global No
metadata_locks_hash_instances Yes Global No
min-examined-row-limit Yes Yes Yes Both Yes
myisam_data_pointer_size Yes Yes Yes Global Yes
myisam_max_sort_file_size Yes Yes Yes Global Yes
myisam_mmap_size Yes Yes Yes Global No
myisam_recover_options Yes Global No
myisam_repair_threads Yes Yes Yes Both Yes
myisam_sort_buffer_size Yes Yes Yes Both Yes
myisam_stats_method Yes Yes Yes Both Yes
myisam_use_mmap Yes Yes Yes Global Yes
named_pipe Yes Global No
net_buffer_length Yes Yes Yes Both Yes
net_read_timeout Yes Yes Yes Both Yes
net_retry_count Yes Yes Yes Both Yes
net_write_timeout Yes Yes Yes Both Yes
new Yes Yes Yes Both Yes
old Yes Yes Yes Global No
old-alter-table Yes Yes Yes
- Variable: old_alter_table Yes Both Yes
old_passwords Yes Both Yes
open-files-limit Yes Yes No
- Variable: open_files_limit Yes Global No
optimizer_prune_level Yes Yes Yes Both Yes
optimizer_search_depth Yes Yes Yes Both Yes
optimizer_switch Yes Yes Yes Both Yes
optimizer_trace Yes Both Yes
optimizer_trace_features Yes Both Yes
optimizer_trace_limit Yes Both Yes
optimizer_trace_max_mem_size Yes Both Yes
optimizer_trace_offset Yes Both Yes
performance_schema Yes Yes Yes Global No
performance_schema_accounts_size Yes Yes Yes Global No
performance_schema_digests_size Yes Yes Yes Global No
performance_schema_events_stages_history_long_size Yes Yes Yes Global No
performance_schema_events_stages_history_size Yes Yes Yes Global No
performance_schema_events_statements_history_long_size Yes Yes Yes Global No
performance_schema_events_statements_history_size Yes Yes Yes Global No
performance_schema_events_waits_history_long_size Yes Yes Yes Global No
performance_schema_events_waits_history_size Yes Yes Yes Global No
performance_schema_hosts_size Yes Yes Yes Global No
performance_schema_max_cond_classes Yes Yes Yes Global No
performance_schema_max_cond_instances Yes Yes Yes Global No
performance_schema_max_file_classes Yes Yes Yes Global No
performance_schema_max_file_handles Yes Yes Yes Global No
performance_schema_max_file_instances Yes Yes Yes Global No
performance_schema_max_mutex_classes Yes Yes Yes Global No
performance_schema_max_mutex_instances Yes Yes Yes Global No
performance_schema_max_rwlock_classes Yes Yes Yes Global No
performance_schema_max_rwlock_instances Yes Yes Yes Global No
performance_schema_max_socket_classes Yes Yes Yes Global No
performance_schema_max_socket_instances Yes Yes Yes Global No
performance_schema_max_stage_classes Yes Yes Yes Global No
performance_schema_max_statement_classes Yes Yes Yes Global No
performance_schema_max_table_handles Yes Yes Yes Global No
performance_schema_max_table_instances Yes Yes Yes Global No
performance_schema_max_thread_classes Yes Yes Yes Global No
performance_schema_max_thread_instances Yes Yes Yes Global No
performance_schema_session_connect_attrs_size Yes Yes Yes Global No
performance_schema_setup_actors_size Yes Yes Yes Global No
performance_schema_setup_objects_size Yes Yes Yes Global No
performance_schema_users_size Yes Yes Yes Global No
pid-file Yes Yes No
- Variable: pid_file Yes Global No
plugin_dir Yes Yes Yes Global No
port Yes Yes Yes Global No
preload_buffer_size Yes Yes Yes Both Yes
profiling Yes Both Yes
profiling_history_size Yes Yes Yes Both Yes
protocol_version Yes Global No
proxy_user Yes Session No
pseudo_slave_mode Yes Session Yes
pseudo_thread_id Yes Session Yes
query_alloc_block_size Yes Yes Yes Both Yes
query_cache_limit Yes Yes Yes Global Yes
query_cache_min_res_unit Yes Yes Yes Global Yes
query_cache_size Yes Yes Yes Global Yes
query_cache_type Yes Yes Yes Both Yes
query_cache_wlock_invalidate Yes Yes Yes Both Yes
query_prealloc_size Yes Yes Yes Both Yes
rand_seed1 Yes Session Yes
rand_seed2 Yes Session Yes
range_alloc_block_size Yes Yes Yes Both Yes
read_buffer_size Yes Yes Yes Both Yes
read_only Yes Yes Yes Global Yes
read_rnd_buffer_size Yes Yes Yes Both Yes
relay-log Yes Yes No
- Variable: relay_log Yes Global No
relay_log_basename Yes Global No
relay-log-index Yes Yes No
- Variable: relay_log_index Yes Global No
relay_log_index Yes Yes Yes Global No
relay_log_info_file Yes Yes Yes Global No
relay_log_info_repository Yes Global Yes
relay_log_purge Yes Yes Yes Global Yes
relay_log_recovery Yes Yes Yes Global Yes
relay_log_space_limit Yes Yes Yes Global No
report-host Yes Yes No
- Variable: report_host Yes Global No
report-password Yes Yes No
- Variable: report_password Yes Global No
report-port Yes Yes No
- Variable: report_port Yes Global No
report-user Yes Yes No
- Variable: report_user Yes Global No
rpl_semi_sync_master_enabled Yes Global Yes
rpl_semi_sync_master_timeout Yes Global Yes
rpl_semi_sync_master_trace_level Yes Global Yes
rpl_semi_sync_master_wait_no_slave Yes Global Yes
rpl_semi_sync_slave_enabled Yes Global Yes
rpl_semi_sync_slave_trace_level Yes Global Yes
secure-auth Yes Yes Yes
- Variable: secure_auth Yes Global Yes
secure-file-priv Yes Yes No
- Variable: secure_file_priv Yes Global No
server-id Yes Yes Yes
- Variable: server_id Yes Global Yes
server_uuid Yes Global No
sha256_password_private_key_path Yes Global No
sha256_password_public_key_path Yes Global No
shared_memory Yes Global No
shared_memory_base_name Yes Global No
skip-external-locking Yes Yes No
- Variable: skip_external_locking Yes Global No
skip-name-resolve Yes Yes No
- Variable: skip_name_resolve Yes Global No
skip-networking Yes Yes No
- Variable: skip_networking Yes Global No
skip-show-database Yes Yes No
- Variable: skip_show_database Yes Global No
slave_allow_batching Yes Yes Yes Global Yes
slave_checkpoint_group Yes Yes Yes Global Yes
slave_checkpoint_period Yes Yes Yes Global Yes
slave_compressed_protocol Yes Yes Yes Global Yes
slave_exec_mode Yes Yes Yes Global Yes
slave-load-tmpdir Yes Yes No
- Variable: slave_load_tmpdir Yes Global No
slave_max_allowed_packet Yes Global Yes
slave-net-timeout Yes Yes Yes
- Variable: slave_net_timeout Yes Global Yes
slave_parallel_workers Yes Global Yes
slave_pending_jobs_size_max Yes Global Yes
slave_rows_search_algorithms Yes Global Yes
slave-skip-errors Yes Yes No
- Variable: slave_skip_errors Yes Global No
slave_sql_verify_checksum Yes Global Yes
slave_transaction_retries Yes Yes Yes Global Yes
slave_type_conversions Yes Yes Yes Global No
slow_launch_time Yes Yes Yes Global Yes
slow-query-log Yes Yes Yes
- Variable: slow_query_log Yes Global Yes
slow_query_log_file Yes Yes Yes Global Yes
socket Yes Yes Yes Global No
sort_buffer_size Yes Yes Yes Both Yes
sql_auto_is_null Yes Both Yes
sql_big_selects Yes Both Yes
sql_big_tables Yes Both Yes
sql_buffer_result Yes Both Yes
sql_log_bin Yes Both Yes
sql_log_off Yes Both Yes
sql-mode Yes Yes Yes
- Variable: sql_mode Yes Both Yes
sql_notes Yes Both Yes
sql_quote_show_create Yes Both Yes
sql_safe_updates Yes Both Yes
sql_select_limit Yes Both Yes
sql_slave_skip_counter Yes Global Yes
sql_warnings Yes Both Yes
ssl-ca Yes Yes No
- Variable: ssl_ca Yes Global No
ssl-capath Yes Yes No
- Variable: ssl_capath Yes Global No
ssl-cert Yes Yes No
- Variable: ssl_cert Yes Global No
ssl-cipher Yes Yes No
- Variable: ssl_cipher Yes Global No
ssl-crl Yes Yes No
- Variable: ssl_crl Yes Global No
ssl-crlpath Yes Yes No
- Variable: ssl_crlpath Yes Global No
ssl-key Yes Yes No
- Variable: ssl_key Yes Global No
storage_engine Yes Both Yes
stored_program_cache Yes Yes Yes Global Yes
sync_binlog Yes Yes Yes Global Yes
sync_frm Yes Yes Yes Global Yes
sync_master_info Yes Yes Yes Global Yes
sync_relay_log Yes Yes Yes Global Yes
sync_relay_log_info Yes Yes Yes Global Yes
system_time_zone Yes Global No
table_definition_cache Yes Global Yes
table_open_cache Yes Global Yes
table_open_cache_instances Yes Global No
thread_cache_size Yes Yes Yes Global Yes
thread_concurrency Yes Yes Yes Global No
thread_handling Yes Yes Yes Global No
thread_stack Yes Yes Yes Global No
time_format Yes Global No
time_zone Yes Both Yes
timed_mutexes Yes Yes Yes Global Yes
timestamp Yes Session Yes
tmp_table_size Yes Yes Yes Both Yes
tmpdir Yes Yes Yes Global No
transaction_alloc_block_size Yes Yes Yes Both Yes
transaction_prealloc_size Yes Yes Yes Both Yes
tx_isolation Yes Both Yes
tx_read_only Yes Both Yes
unique_checks Yes Both Yes
updatable_views_with_limit Yes Yes Yes Both Yes
validate_password_dictionary_file Yes Global No
validate_password_length Yes Global Yes
validate_password_mixed_case_count Yes Global Yes
validate_password_number_count Yes Global Yes
validate_password_policy Yes Global Yes
validate_password_special_char_count Yes Global Yes
validate_user_plugins Yes Global No
version Yes Global No
version_comment Yes Global No
version_compile_machine Yes Global No
version_compile_os Yes Global No
wait_timeout Yes Yes Yes Both Yes
warning_count Yes Session No

[a] This option is dynamic, but only the server should set this information. You should not set the value of this variable manually.

[b] This option is dynamic, but only the server should set this information. You should not set the value of this variable manually.


For additional system variable information, see these sections:

Note

Some of the following variable descriptions refer to "enabling" or "disabling" a variable. These variables can be enabled with the SET statement by setting them to ON or 1, or disabled by setting them to OFF or 0. In MySQL 5.7, boolean variables can be set at startup to the values ON, TRUE, OFF, and FALSE (not case sensitive), as well as 1 and 0. See Section 4.2.3.2, "Program Option Modifiers".

Some system variables control the size of buffers or caches. For a given buffer, the server might need to allocate internal data structures. These structures typically are allocated from the total memory allocated to the buffer, and the amount of space required might be platform dependent. This means that when you assign a value to a system variable that controls a buffer size, the amount of space actually available might differ from the value assigned. In some cases, the amount might be less than the value assigned. It is also possible that the server will adjust a value upward. For example, if you assign a value of 0 to a variable for which the minimal value is 1024, the server will set the value to 1024.

Values for buffer sizes, lengths, and stack sizes are given in bytes unless otherwise specified.

Some system variables take file name values. Unless otherwise specified, the default file location is the data directory if the value is a relative path name. To specify the location explicitly, use an absolute path name. Suppose that the data directory is /var/mysql/data. If a file-valued variable is given as a relative path name, it will be located under /var/mysql/data. If the value is an absolute path name, its location is as given by the path name.