|
|
| Applications |
| Mailing Lists |
| Miscellaneous |
| Operating Systems |
| Programming |
Skip navigation links
MySQL 5.1 Reference Manual :: 5 MySQL Server Administration :: 5.1 The MySQL Server :: 5.1.3 System Variables
Section Navigation [Toggle]
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:
To see the values that a server will use based on its compiled-in defaults and any option files that it reads, use this command:
mysqld --verbose --help
To see the values that a server will use based on its compiled-in defaults, ignoring the settings in any option files, use this command:
mysqld --no-defaults --verbose --help
To see the current values used by a running server, use the
SHOW VARIABLESstatement.
This section provides a description of each system variable. Variables with no version indicated are present in all MySQL 5.1 releases. For historical information concerning their implementation, please see MySQL 5.0 Reference Manual and MySQL 3.23, 4.0, 4.1 Reference Manual.
The following table lists all available system variables:
| Name | Cmd-Line | Option file | System Var | Status Var | Var Scope | Dynamic |
|---|---|---|---|---|---|---|
| autocommit | Â | Â | Yes | Â | Session | Yes |
| auto-increment-increment | Yes | Yes | Â | Â | Both | Yes |
| - Variable: auto_increment_increment | Â | Â | Yes | Â | Both | Yes |
| auto-increment-offset | Yes | Yes | Â | Â | Both | Yes |
| - Variable: auto_increment_offset | Â | Â | Yes | Â | Both | Yes |
| automatic_sp_privileges | Â | Â | Yes | Â | Global | Yes |
| back_log | Yes | Yes | Yes | Â | Global | No |
| basedir | Yes | Yes | Yes | Â | Global | No |
| big-tables | Yes | Yes | Â | Â | Session | Yes |
| - Variable: big_tables | Â | Â | Yes | Â | Session | Yes |
| binlog_cache_size | Yes | Yes | Yes | Â | Global | Yes |
| binlog-format | Yes | Yes | Â | Â | Both | Yes |
| - Variable: binlog_format | Â | Â | Yes | Â | Both | Yes |
| bulk_insert_buffer_size | Yes | Yes | Yes | Â | Both | Yes |
| character_set_client | Â | Â | Yes | Â | Both | Yes |
| character_set_connection | Â | Â | Yes | Â | Both | Yes |
| character_set_database | Â | Â | Yes | Â | Both | Yes |
| character-set-filesystem | Yes | Yes | Â | Â | Both | Yes |
| - Variable: character_set_filesystem | Â | Â | Yes | Â | Both | Yes |
| character_set_results | Â | Â | Yes | Â | Both | Yes |
| character-sets-dir | Yes | Yes | Â | Â | Global | No |
| - Variable: character_sets_dir | Â | Â | Yes | Â | Global | No |
| character-set-server | Yes | Yes | Â | Â | Both | Yes |
| - Variable: character_set_server | Â | Â | Yes | Â | Both | Yes |
| character_set_system | Â | Â | Yes | Â | Global | No |
| collation_connection | Â | Â | Yes | Â | Both | Yes |
| collation_database | Â | Â | Yes | Â | Both | Yes |
| collation-server | Yes | Yes | Â | Â | Both | Yes |
| - Variable: collation_server | Â | Â | Yes | Â | Both | Yes |
| completion_type | Yes | Yes | Yes | Â | Both | Yes |
| concurrent_insert | Yes | Yes | Yes | Â | Global | Yes |
| connect_timeout | Yes | Yes | Yes | Â | Global | Yes |
| datadir | Yes | Yes | Yes | Â | Global | No |
| date_format | Â | Â | Yes | Â | Both | Yes |
| datetime_format | Yes | Yes | Yes | Â | Both | Yes |
| debug | Yes | Yes | Yes | Â | Both | Yes |
| default_week_format | Yes | Yes | Yes | Â | Both | Yes |
| delayed_insert_limit | Yes | Yes | Yes | Â | Global | Yes |
| delayed_insert_timeout | Yes | Yes | Yes | Â | Global | Yes |
| delayed_queue_size | Yes | Yes | Yes | Â | Global | Yes |
| delay-key-write | Yes | Yes | Â | Â | Global | Yes |
| - Variable: delay_key_write | Â | Â | Yes | Â | Global | Yes |
| div_precision_increment | Yes | Yes | Yes | Â | Both | Yes |
| engine-condition-pushdown | Yes | Yes | Â | Â | Both | Yes |
| - Variable: engine_condition_pushdown | Â | Â | Yes | Â | Both | Yes |
| error_count | Â | Â | Yes | Â | Session | No |
| event-scheduler | Yes | Yes | Yes | Â | Global | Yes |
| expire_logs_days | Yes | Yes | Yes | Â | Global | Yes |
| flush | Yes | Yes | Yes | Â | Global | Yes |
| flush_time | Yes | Yes | Yes | Â | Global | Yes |
| foreign_key_checks | Â | Â | Yes | Â | Session | Yes |
| ft_boolean_syntax | Yes | Yes | Yes | Â | Global | Yes |
| ft_max_word_len | Yes | Yes | Yes | Â | Global | No |
| ft_min_word_len | Yes | Yes | Yes | Â | Global | No |
| ft_query_expansion_limit | Yes | Yes | Yes | Â | Global | No |
| ft_stopword_file | Yes | Yes | Yes | Â | Global | No |
| general-log | Yes | Yes | Â | Â | Global | Yes |
| - Variable: general_log | Â | Â | Yes | Â | Global | Yes |
| general_log_file | Â | Â | Yes | Â | Global | Yes |
| group_concat_max_len | Yes | Yes | Yes | Â | Both | Yes |
| have_archive | Â | Â | Yes | Â | Global | No |
| have_blackhole_engine | Â | Â | Yes | Â | Global | No |
| have_compress | Â | Â | Yes | Â | Global | No |
| have_crypt | Â | Â | Yes | Â | Global | No |
| have_csv | Â | Â | Yes | Â | Global | No |
| have_dynamic_loading | Â | Â | Yes | Â | Global | No |
| have_example_engine | Â | Â | Yes | Â | Global | No |
| have_federated_engine | Â | Â | Yes | Â | Global | No |
| have_geometry | Â | Â | Yes | Â | Global | No |
| have_innodb | Â | Â | Yes | Â | Global | No |
| have_isam | Â | Â | Yes | Â | Global | No |
| have_merge_engine | Â | Â | Yes | Â | Global | No |
| have_ndbcluster | Â | Â | Yes | Â | Global | No |
| have_openssl | Â | Â | Yes | Â | Global | No |
| have_partitioning | Â | Â | Yes | Â | Global | No |
| have_query_cache | Â | Â | Yes | Â | Global | No |
| have_raid | Â | Â | Yes | Â | Global | No |
| have_row_based_replication | Â | Â | Yes | Â | Global | No |
| have_rtree_keys | Â | Â | Yes | Â | Global | No |
| have_ssl | Â | Â | Yes | Â | Global | No |
| have_symlink | Â | Â | Yes | Â | Global | No |
| hostname | Â | Â | Yes | Â | Global | No |
| identity | Â | Â | Yes | Â | Session | Yes |
| init_connect | Yes | Yes | Yes | Â | Global | Yes |
| init-file | Yes | Yes | Â | Â | Global | No |
| - Variable: init_file | Â | Â | Yes | Â | Global | No |
| init_slave | Yes | Yes | Yes | Â | Global | Yes |
| innodb_adaptive_hash_index | Yes | Yes | Yes | Â | Global | No |
| innodb_additional_mem_pool_size | Yes | Yes | Yes | Â | Global | No |
| innodb_autoextend_increment | Yes | Yes | Yes | Â | Global | Yes |
| innodb_autoinc_lock_mode | Yes | Yes | Yes | Â | Global | No |
| innodb_buffer_pool_awe_mem_mb | Yes | Yes | Yes | Â | Global | No |
| innodb_buffer_pool_size | Yes | Yes | Yes | Â | Global | No |
| innodb_checksums | Yes | Yes | Yes | Â | Global | No |
| innodb_commit_concurrency | Yes | Yes | Yes | Â | Global | Yes |
| innodb_concurrency_tickets | Yes | Yes | Yes | Â | Global | Yes |
| innodb_data_file_path | Yes | Yes | Yes | Â | Global | No |
| innodb_data_home_dir | Yes | Yes | Yes | Â | Global | No |
| innodb_doublewrite | Yes | Yes | Yes | Â | Global | No |
| innodb_fast_shutdown | Yes | Yes | Yes | Â | Global | Yes |
| innodb_file_io_threads | Yes | Yes | Yes | Â | Global | No |
| innodb_file_per_table | Yes | Yes | Yes | Â | Global | No |
| innodb_flush_log_at_trx_commit | Yes | Yes | Yes | Â | Global | Yes |
| innodb_flush_method | Yes | Yes | Yes | Â | Global | No |
| innodb_force_recovery | Yes | Yes | Yes | Â | Global | No |
| innodb_locks_unsafe_for_binlog | Yes | Yes | Yes | Â | Global | No |
| innodb_lock_wait_timeout | Yes | Yes | Yes | Â | Global | No |
| innodb_log_arch_dir | Yes | Yes | Yes | Â | Global | No |
| innodb_log_archive | Yes | Yes | Yes | Â | Global | No |
| innodb_log_buffer_size | Yes | Yes | Yes | Â | Global | No |
| innodb_log_files_in_group | Yes | Yes | Yes | Â | Global | No |
| innodb_log_file_size | Yes | Yes | Yes | Â | Global | No |
| innodb_log_group_home_dir | Yes | Yes | Yes | Â | Global | No |
| innodb_max_dirty_pages_pct | Yes | Yes | Yes | Â | Global | Yes |
| innodb_max_purge_lag | Yes | Yes | Yes | Â | Global | Yes |
| innodb_mirrored_log_groups | Yes | Yes | Yes | Â | Global | No |
| innodb_open_files | Yes | Yes | Yes | Â | Global | No |
| innodb_rollback_on_timeout | Yes | Yes | Yes | Â | Global | No |
| innodb_stats_on_metadata | Yes | Yes | Yes | Â | Global | No |
| innodb_status_file | Yes | Yes | Yes | Â | Global | No |
| innodb_support_xa | Yes | Yes | Yes | Â | Both | Yes |
| innodb_sync_spin_loops | Yes | Yes | Yes | Â | Global | Yes |
| innodb_table_locks | Yes | Yes | Yes | Â | Both | Yes |
| innodb_thread_concurrency | Yes | Yes | Yes | Â | Global | Yes |
| innodb_thread_sleep_delay | Yes | Yes | Yes | Â | Global | Yes |
| insert_id | Â | Â | Yes | Â | Session | Yes |
| interactive_timeout | Yes | Yes | Yes | Â | Both | Yes |
| join_buffer_size | Yes | Yes | Yes | Â | Both | Yes |
| keep_files_on_create | Yes | Yes | Yes | Â | Both | Yes |
| key_buffer_size | Yes | Yes | Yes | Â | Global | Yes |
| key_cache_age_threshold | Yes | Yes | Yes | Â | Global | Yes |
| key_cache_block_size | Yes | Yes | Yes | Â | Global | Yes |
| key_cache_division_limit | Yes | Yes | Yes | Â | Global | Yes |
| language | Yes | Yes | Yes | Â | Global | No |
| large-pages | Yes | Yes | Â | Â | Global | No |
| - Variable: large_pages | Â | Â | Yes | Â | Global | No |
| large_page_size | Â | Â | Yes | Â | Global | No |
| last_insert_id | Â | Â | Yes | Â | Session | Yes |
| lc_time_names | Â | Â | Yes | Â | Both | Yes |
| license | Â | Â | Yes | Â | Global | No |
| local_infile | Â | Â | Yes | Â | Global | Yes |
| locked_in_memory | Â | Â | Yes | Â | Global | No |
| log | Yes | Yes | Yes | Â | Global | Yes |
| log_bin | Â | Â | Yes | Â | Global | No |
| log-bin-trust-function-creators | Yes | Yes | Â | Â | Global | Yes |
| - Variable: log_bin_trust_function_creators | Â | Â | Yes | Â | Global | Yes |
| log-bin-trust-routine-creators | Yes | Yes | Â | Â | Global | Yes |
| - Variable: log_bin_trust_routine_creators | Â | Â | Yes | Â | Global | Yes |
| log-error | Yes | Yes | Â | Â | Global | No |
| - Variable: log_error | Â | Â | Yes | Â | Global | No |
| log-output | Yes | Yes | Â | Â | Global | Yes |
| - Variable: log_output | Â | Â | Yes | Â | Global | Yes |
| log-queries-not-using-indexes | Yes | Yes | Â | Â | Global | Yes |
| - Variable: log_queries_not_using_indexes | Â | Â | Yes | Â | Global | Yes |
| log-slave-updates | Yes | Yes | Â | Â | Global | No |
| - Variable: log_slave_updates | Â | Â | Yes | Â | Global | No |
| log-slow-queries | Yes | Yes | Â | Â | Global | Yes |
| - Variable: log_slow_queries | Â | Â | Yes | Â | Global | Yes |
| log-warnings | Yes | Yes | Â | Â | Both | Yes |
| - Variable: log_warnings | Â | Â | Yes | Â | Both | Yes |
| long_query_time | Yes | Yes | Yes | Â | Both | Yes |
| lower_case_file_system | Yes | Yes | Yes | Â | Global | No |
| lower_case_table_names | Yes | Yes | Yes | Â | Global | No |
| low-priority-updates | Yes | Yes | Â | Â | Both | Yes |
| - Variable: low_priority_updates | Â | Â | Yes | Â | Both | Yes |
| master-bind | Yes | Yes | Yes | Â | Â | No |
| max_allowed_packet | Yes | Yes | Yes | Â | Both | Yes |
| max_binlog_cache_size | Yes | Yes | Yes | Â | Global | Yes |
| max_binlog_size | Yes | Yes | Yes | Â | Global | Yes |
| max_connect_errors | Yes | Yes | Yes | Â | Global | Yes |
| max_connections | Yes | Yes | Yes | Â | Global | Yes |
| max_delayed_threads | Yes | Yes | Yes | Â | Both | Yes |
| max_error_count | Yes | Yes | Yes | Â | Both | Yes |
| max_heap_table_size | Yes | Yes | Yes | Â | Both | Yes |
| max_insert_delayed_threads | Â | Â | Yes | Â | Both | Yes |
| max_join_size | Yes | Yes | Yes | Â | Both | Yes |
| max_length_for_sort_data | Yes | Yes | Yes | Â | Both | Yes |
| max_prepared_stmt_count | Yes | Yes | Yes | Â | Global | Yes |
| max_relay_log_size | Yes | Yes | Yes | Â | Global | Yes |
| max_seeks_for_key | Yes | Yes | Yes | Â | Both | Yes |
| max_sort_length | Yes | Yes | Yes | Â | Both | Yes |
| max_sp_recursion_depth | Yes | Yes | Yes | Â | Both | Yes |
| max_tmp_tables | Yes | Yes | Yes | Â | Both | Yes |
| max_user_connections | Yes | Yes | Yes | Â | Both | Yes |
| max_write_lock_count | Yes | Yes | Yes | Â | Global | Yes |
| memlock | Yes | Yes | Yes | Â | Global | No |
| min-examined-row-limit | Yes | Yes | Yes | Â | Both | Yes |
| multi_range_count | Yes | Yes | Yes | Â | Both | Yes |
| myisam_block_size | Yes | Yes | Yes | Â | Both | Yes |
| myisam_data_pointer_size | Yes | Yes | Yes | Â | Global | Yes |
| myisam_max_sort_file_size | Yes | Yes | Yes | Â | Global | Yes |
| myisam_recover_options | Â | Â | Yes | Â | Global | No |
| myisam_repair_threads | Yes | Yes | Yes | Â | Both | Yes |
| myisam_sort_buffer_size | Yes | Yes | Yes | Â | Both | Yes |
| myisam_stats_method | Yes | Yes | Yes | Â | Both | Yes |
| myisam_use_mmap | Yes | Yes | Yes | Â | Global | Yes |
| named_pipe | Â | Â | Yes | Â | Global | No |
| ndb_autoincrement_prefetch_sz | Yes | Yes | Yes | Â | Both | Yes |
| ndb_cache_check_time | Yes | Yes | Yes | Â | Global | Yes |
| ndbcluster | Yes | Yes | Yes | Â | Both | Yes |
| ndb_extra_logging | Yes | Yes | Yes | Â | Global | Yes |
| ndb_force_send | Yes | Yes | Yes | Â | Both | Yes |
| ndb_log_orig | Â | Â | Yes | Â | Global | No |
| ndb_log_update_as_write | Yes | Yes | Yes | Â | Global | Yes |
| ndb_log_updated_only | Yes | Yes | Yes | Â | Global | Yes |
| ndb_optimization_delay | Â | Â | Yes | Â | Global | Yes |
| ndb_table_no_logging | Â | Â | Yes | Â | Session | Yes |
| ndb_table_temporary | Â | Â | Yes | Â | Session | Yes |
| ndb_use_copying_alter_table | Â | Â | Yes | Â | Both | No |
| ndb_use_exact_count | Â | Â | Yes | Â | Both | Yes |
| ndb_wait_connected | Yes | Yes | Yes | Â | Â | No |
| net_buffer_length | Yes | Yes | Yes | Â | Both | Yes |
| net_read_timeout | Yes | Yes | Yes | Â | Both | Yes |
| net_retry_count | Yes | Yes | Yes | Â | Both | Yes |
| net_write_timeout | Yes | Yes | Yes | Â | Both | Yes |
| new | Yes | Yes | Yes | Â | Both | Yes |
| old | Yes | Yes | Yes | Â | Global | No |
| old-passwords | Yes | Yes | Â | Â | Both | Yes |
| - Variable: old_passwords | Â | Â | Yes | Â | Both | Yes |
| open-files-limit | Yes | Yes | Â | Â | Global | No |
| - Variable: open_files_limit | Â | Â | Yes | Â | Global | No |
| optimizer_prune_level | Yes | Yes | Yes | Â | Both | Yes |
| optimizer_search_depth | Yes | Yes | Yes | Â | Both | Yes |
| pid-file | Yes | Yes | Â | Â | Global | No |
| - Variable: pid_file | Â | Â | Yes | Â | Global | No |
| plugin_dir | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_additional_mem_pool_size | Yes | Yes | Yes | Â | Both | No |
| plugin_innodb_autoextend_increment | Yes | Yes | Yes | Â | Both | Yes |
| plugin_innodb_buffer_pool_awe_mem_mb | Yes | Yes | Â | Â | Both | No |
| - Variable: innodb_buffer_pool_awe_mem_mb | Â | Â | Yes | Â | Both | No |
| plugin_innodb_buffer_pool_size | Yes | Yes | Yes | Â | Both | No |
| plugin_innodb_checksums | Yes | Yes | Yes | Â | Both | Yes |
| plugin_innodb_commit_concurrency | Yes | Yes | Yes | Â | Global | Yes |
| plugin_innodb_concurrency_tickets | Yes | Yes | Yes | Â | Global | Yes |
| plugin_innodb_data_file_path | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_data_home_dir | Yes | Yes | Yes | Â | Global | No |
| plugin-innodb-doublewrite | Yes | Yes | Â | Â | Global | No |
| - Variable: plugin_innodb_doublewrite | Â | Â | Yes | Â | Global | No |
| plugin_innodb_fast_shutdown | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_file_io_threads | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_file_per_table | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_flush_log_at_trx_commit | Yes | Yes | Yes | Â | Global | Yes |
| plugin_innodb_flush_method | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_force_recovery | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_locks_unsafe_for_binlog | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_lock_wait_timeout | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_log_archive | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_log_buffer_size | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_log_files_in_group | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_log_file_size | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_log_group_home_dir | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_max_dirty_pages_pct | Yes | Yes | Yes | Â | Global | Yes |
| plugin_innodb_max_purge_lag | Yes | Yes | Yes | Â | Global | Yes |
| plugin_innodb_mirrored_log_groups | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_open_files | Yes | Yes | Yes | Â | Global | No |
| plugin_innodb_rollback_on_timeout | Yes | Yes | Yes | Â | Â | No |
| plugin_innodb_stats_on_metadata | Yes | Yes | Yes | Â | Â | No |
| plugin_innodb_status_file | Yes | Yes | Yes | Â | Â | No |
| plugin_innodb_support_xa | Yes | Yes | Yes | Â | Both | Yes |
| plugin_innodb_sync_spin_loops | Yes | Yes | Yes | Â | Global | Yes |
| plugin_innodb_table_locks | Yes | Yes | Yes | Â | Both | Yes |
| plugin_innodb_thread_concurrency | Yes | Yes | Yes | Â | Global | Yes |
| plugin_innodb_thread_sleep_delay | Yes | Yes | Yes | Â | Global | Yes |
| port | Yes | Yes | Yes | Â | Global | No |
| preload_buffer_size | Yes | Yes | Yes | Â | Both | Yes |
| prepared_stmt_count | Â | Â | Yes | Yes | Global | No |
| protocol_version | Â | Â | Yes | Â | Global | No |
| query_alloc_block_size | Yes | Yes | Yes | Â | Both | Yes |
| query_cache_limit | Yes | Yes | Yes | Â | Global | Yes |
| query_cache_min_res_unit | Yes | Yes | Yes | Â | Global | Yes |
| query_cache_size | Yes | Yes | Yes | Â | Global | Yes |
| query_cache_type | Yes | Yes | Yes | Â | Both | Yes |
| query_cache_wlock_invalidate | Yes | Yes | Yes | Â | Both | Yes |
| query_prealloc_size | Yes | Yes | Yes | Â | Both | Yes |
| range_alloc_block_size | Yes | Yes | Yes | Â | Both | Yes |
| read_buffer_size | Yes | Yes | Yes | Â | Both | Yes |
| read_only | Yes | Yes | Yes | Â | Global | Yes |
| read_rnd_buffer_size | Yes | Yes | Yes | Â | Both | Yes |
| relay_log_purge | Yes | Yes | Yes | Â | Global | Yes |
| relay_log_space_limit | Yes | Yes | Yes | Â | Global | No |
| report-host | Yes | Yes | Â | Â | Global | No |
| - Variable: report_host | Â | Â | Yes | Â | Global | No |
| report-password | Yes | Yes | Â | Â | Global | No |
| - Variable: report_password | Â | Â | Yes | Â | Global | No |
| report-port | Yes | Yes | Â | Â | Global | No |
| - Variable: report_port | Â | Â | Yes | Â | Global | No |
| report-user | Yes | Yes | Â | Â | Global | No |
| - Variable: report_user | Â | Â | Yes | Â | Global | No |
| rpl_recovery_rank | Â | Â | Yes | Â | Global | Yes |
| secure-auth | Yes | Yes | Â | Â | Global | Yes |
| - Variable: secure_auth | Â | Â | Yes | Â | Global | Yes |
| secure-file-priv | Yes | Yes | Â | Â | Global | No |
| - Variable: secure_file_priv | Â | Â | Yes | Â | Global | No |
| server-id | Yes | Yes | Â | Â | Global | Yes |
| - Variable: server_id | Â | Â | Yes | Â | Global | Yes |
| shared_memory | Â | Â | Yes | Â | Global | No |
| shared_memory_base_name | Â | Â | Yes | Â | Global | No |
| skip-external-locking | Yes | Yes | Â | Â | Global | No |
| - Variable: skip_external_locking | Â | Â | Yes | Â | Global | No |
| skip-networking | Yes | Yes | Â | Â | Global | No |
| - Variable: skip_networking | Â | Â | Yes | Â | Global | No |
| skip-show-database | Yes | Yes | Â | Â | Global | No |
| - Variable: skip_show_database | Â | Â | Yes | Â | Global | No |
| slave-allow-batching | Yes | Â | Â | Â | Global | Yes |
| - Variable: slave_allow_batching | Â | Â | Yes | Â | Global | Yes |
| slave_compressed_protocol | Yes | Yes | Yes | Â | Global | Yes |
| slave_exec_mode | Â | Â | Yes | Â | Global | Yes |
| slave-load-tmpdir | Yes | Yes | Â | Â | Global | No |
| - Variable: slave_load_tmpdir | Â | Â | Yes | Â | Global | No |
| slave-net-timeout | Yes | Yes | Â | Â | Global | Yes |
| - Variable: slave_net_timeout | Â | Â | Yes | Â | Global | Yes |
| slave-skip-errors | Yes | Yes | Â | Â | Global | No |
| - Variable: slave_skip_errors | Â | Â | Yes | Â | Global | No |
| slave_transaction_retries | Yes | Yes | Yes | Â | Global | Yes |
| slow_launch_time | Yes | Yes | Yes | Â | Global | Yes |
| slow-query-log | Yes | Yes | Â | Â | Global | Yes |
| - Variable: slow_query_log | Â | Â | Yes | Â | Global | Yes |
| slow_query_log_file | Â | Â | Yes | Â | Global | Yes |
| socket | Yes | Yes | Yes | Â | Global | No |
| sort_buffer_size | Yes | Yes | Yes | Â | Both | Yes |
| sql_auto_is_null | Â | Â | Yes | Â | Session | Yes |
| sql_big_selects | Â | Â | Yes | Â | Session | Yes |
| sql_big_tables | Â | Â | Yes | Â | Session | Yes |
| sql_buffer_result | Â | Â | Yes | Â | Session | Yes |
| sql_log_bin | Â | Â | Yes | Â | Session | Yes |
| sql_log_off | Â | Â | Yes | Â | Session | Yes |
| sql_log_update | Â | Â | Yes | Â | Session | Yes |
| sql_low_priority_updates | Â | Â | Yes | Â | Both | Yes |
| sql_max_join_size | Â | Â | Yes | Â | Both | Yes |
| sql-mode | Yes | Yes | Â | Â | Both | Yes |
| - Variable: sql_mode | Â | Â | Yes | Â | Both | Yes |
| sql_notes | Â | Â | Yes | Â | Session | Yes |
| sql_quote_show_create | Â | Â | Yes | Â | Session | Yes |
| sql_safe_updates | Â | Â | Yes | Â | Session | Yes |
| sql_select_limit | Yes | Yes | Yes | Â | Both | Yes |
| sql_slave_skip_counter | Â | Â | Yes | Â | Global | Yes |
| sql_warnings | Â | Â | Yes | Â | Session | Yes |
| ssl-ca | Yes | Yes | Â | Â | Global | No |
| - Variable: ssl_ca | Â | Â | Yes | Â | Global | No |
| ssl-capath | Yes | Yes | Â | Â | Global | No |
| - Variable: ssl_capath | Â | Â | Yes | Â | Global | No |
| ssl-cert | Yes | Yes | Â | Â | Global | No |
| - Variable: ssl_cert | Â | Â | Yes | Â | Global | No |
| ssl-cipher | Yes | Yes | Â | Â | Global | No |
| - Variable: ssl_cipher | Â | Â | Yes | Â | Global | No |
| ssl-key | Yes | Yes | Â | Â | Global | No |
| - Variable: ssl_key | Â | Â | Yes | Â | Global | No |
| storage_engine | Â | Â | Yes | Â | Both | Yes |
| sync-binlog | Yes | Yes | Â | Â | Global | Yes |
| - Variable: sync_binlog | Â | Â | Yes | Â | Global | Yes |
| sync-frm | Yes | Yes | Â | Â | Global | Yes |
| - Variable: sync_frm | Â | Â | Yes | Â | Global | Yes |
| system_time_zone | Â | Â | Yes | Â | Global | No |
| table_cache | Yes | Yes | Yes | Â | Global | Yes |
| table_definition_cache | Yes | Yes | Yes | Â | Global | Yes |
| table_lock_wait_timeout | Yes | Yes | Yes | Â | Global | Yes |
| table_open_cache | Â | Yes | Yes | Â | Global | Yes |
| table_type | Â | Â | Yes | Â | Both | Yes |
| thread_cache_size | Yes | Yes | Yes | Â | Global | Yes |
| thread_concurrency | Yes | Yes | Yes | Â | Global | No |
| thread_handling | Yes | Yes | Yes | Â | Global | No |
| thread_stack | Yes | Yes | Yes | Â | Global | No |
| timed_mutexes | Yes | Yes | Yes | Â | Global | Yes |
| time_format | Yes | Yes | Yes | Â | Both | Yes |
| timestamp | Â | Â | Yes | Â | Session | Yes |
| time_zone | Yes | Â | Yes | Â | Both | Yes |
| tmpdir | Yes | Yes | Yes | Â | Global | No |
| tmp_table_size | Yes | Yes | Yes | Â | Both | Yes |
| transaction_alloc_block_size | Yes | Yes | Yes | Â | Both | Yes |
| transaction_allow_batching | Â | Â | Yes | Â | Session | Yes |
| transaction_prealloc_size | Yes | Yes | Yes | Â | Both | Yes |
| tx_isolation | Â | Â | Yes | Â | Both | Yes |
| unique_checks | Â | Â | Yes | Â | Session | Yes |
| updatable_views_with_limit | Yes | Yes | Yes | Â | Both | Yes |
| version | Yes | Â | Yes | Â | Global | No |
| version_comment | Â | Â | Yes | Â | Global | No |
| version_compile_machine | Â | Â | Yes | Â | Global | No |
| version_compile_os | Â | Â | Yes | Â | Global | No |
| wait_timeout | Yes | Yes | Yes | Â | Both | Yes |
| warning_count | Â | Â | Yes | Â | Session | No |
For additional system variable information, see these sections:
Section 5.1.4, “Session System Variablesâ€, describes system variables that exist only as session variables (that is, they do not have any global counterpart).
Section 5.1.5, “Using System Variablesâ€, discusses the syntax for setting and displaying system variable values.
Section 5.1.5.2, “Dynamic System Variablesâ€, lists the variables that can be set at runtime.
Information on tuning system variables can be found in Section 7.5.2, “Tuning Server Parametersâ€.
Section 13.5.4, “
InnoDBStartup Options and System Variablesâ€, listsInnoDBsystem variables.
Note
Some of the following variable descriptions refer to “enabling†or “disabling†a variable. These variables can be enabled with the