5.1.6. Server Status Variables

The server maintains many status variables that provide information about its operation. You can view these variables and their values by using the SHOW [GLOBAL | SESSION] STATUS statement (see Section 12.4.5.36, “SHOW STATUS Syntax”). The optional GLOBAL keyword aggregates the values over all connections, and SESSION shows the values for the current connection.

mysql> SHOW GLOBAL STATUS;
+-----------------------------------+------------+
| Variable_name                     | Value      |
+-----------------------------------+------------+
| Aborted_clients                   | 0          |
| Aborted_connects                  | 0          |
| Bytes_received                    | 155372598  |
| Bytes_sent                        | 1176560426 |
...
| Connections                       | 30023      |
| Created_tmp_disk_tables           | 0          |
| Created_tmp_files                 | 3          |
| Created_tmp_tables                | 2          |
...
| Threads_created                   | 217        |
| Threads_running                   | 88         |
| Uptime                            | 1389872    |
+-----------------------------------+------------+

The following table lists all available server status variables:

Table 5.4. Status Variable Summary

Variable NameVariable TypeVariable Scope
Aborted_clientsnumericGLOBAL
Aborted_connectsnumericGLOBAL
Binlog_cache_disk_usenumericGLOBAL
Binlog_cache_usenumericGLOBAL
Binlog_stmt_cache_disk_usenumericGLOBAL
Binlog_stmt_cache_usenumericGLOBAL
Bytes_receivednumericGLOBAL | SESSION
Bytes_sentnumericGLOBAL | SESSION
Com_admin_commandsnumericGLOBAL | SESSION
Com_alter_dbnumericGLOBAL | SESSION
Com_alter_db_upgradenumericGLOBAL | SESSION
Com_alter_eventnumericGLOBAL | SESSION
Com_alter_functionnumericGLOBAL | SESSION
Com_alter_procedurenumericGLOBAL | SESSION
Com_alter_servernumericGLOBAL | SESSION
Com_alter_tablenumericGLOBAL | SESSION
Com_alter_tablespacenumericGLOBAL | SESSION
Com_analyzenumericGLOBAL | SESSION
Com_assign_to_keycachenumericGLOBAL | SESSION
Com_backup_tablenumericGLOBAL | SESSION
Com_beginnumericGLOBAL | SESSION
Com_binlognumericGLOBAL | SESSION
Com_call_procedurenumericGLOBAL | SESSION
Com_change_dbnumericGLOBAL | SESSION
Com_change_masternumericGLOBAL | SESSION
Com_checknumericGLOBAL | SESSION
Com_checksumnumericGLOBAL | SESSION
Com_commitnumericGLOBAL | SESSION
Com_create_dbnumericGLOBAL | SESSION
Com_create_eventnumericGLOBAL | SESSION
Com_create_functionnumericGLOBAL | SESSION
Com_create_indexnumericGLOBAL | SESSION
Com_create_procedurenumericGLOBAL | SESSION
Com_create_servernumericGLOBAL | SESSION
Com_create_tablenumericGLOBAL | SESSION
Com_create_triggernumericGLOBAL | SESSION
Com_create_udfnumericGLOBAL | SESSION
Com_create_usernumericGLOBAL | SESSION
Com_create_viewnumericGLOBAL | SESSION
Com_dealloc_sqlnumericGLOBAL | SESSION
Com_deletenumericGLOBAL | SESSION
Com_delete_multinumericGLOBAL | SESSION
Com_donumericGLOBAL | SESSION
Com_drop_dbnumericGLOBAL | SESSION
Com_drop_eventnumericGLOBAL | SESSION
Com_drop_functionnumericGLOBAL | SESSION
Com_drop_indexnumericGLOBAL | SESSION
Com_drop_procedurenumericGLOBAL | SESSION
Com_drop_servernumericGLOBAL | SESSION
Com_drop_tablenumericGLOBAL | SESSION
Com_drop_triggernumericGLOBAL | SESSION
Com_drop_usernumericGLOBAL | SESSION
Com_drop_viewnumericGLOBAL | SESSION
Com_empty_querynumericGLOBAL | SESSION
Com_execute_sqlnumericGLOBAL | SESSION
Com_flushnumericGLOBAL | SESSION
Com_grantnumericGLOBAL | SESSION
Com_ha_closenumericGLOBAL | SESSION
Com_ha_opennumericGLOBAL | SESSION
Com_ha_readnumericGLOBAL | SESSION
Com_helpnumericGLOBAL | SESSION
Com_insertnumericGLOBAL | SESSION
Com_insert_selectnumericGLOBAL | SESSION
Com_install_pluginnumericGLOBAL | SESSION
Com_killnumericGLOBAL | SESSION
Com_loadnumericGLOBAL | SESSION
Com_lock_tablesnumericGLOBAL | SESSION
Com_optimizenumericGLOBAL | SESSION
Com_preload_keysnumericGLOBAL | SESSION
Com_prepare_sqlnumericGLOBAL | SESSION
Com_purgenumericGLOBAL | SESSION
Com_purge_before_datenumericGLOBAL | SESSION
Com_release_savepointnumericGLOBAL | SESSION
Com_rename_tablenumericGLOBAL | SESSION
Com_rename_usernumericGLOBAL | SESSION
Com_repairnumericGLOBAL | SESSION
Com_replacenumericGLOBAL | SESSION
Com_replace_selectnumericGLOBAL | SESSION
Com_resetnumericGLOBAL | SESSION
Com_resignalnumericGLOBAL | SESSION
Com_restore_tablenumericGLOBAL | SESSION
Com_revokenumericGLOBAL | SESSION
Com_revoke_allnumericGLOBAL | SESSION
Com_rollbacknumericGLOBAL | SESSION
Com_rollback_to_savepointnumericGLOBAL | SESSION
Com_savepointnumericGLOBAL | SESSION
Com_selectnumericGLOBAL | SESSION
Com_set_optionnumericGLOBAL | SESSION
Com_show_authorsnumericGLOBAL | SESSION
Com_show_binlog_eventsnumericGLOBAL | SESSION
Com_show_binlogsnumericGLOBAL | SESSION
Com_show_charsetsnumericGLOBAL | SESSION
Com_show_collationsnumericGLOBAL | SESSION
Com_show_column_typesnumericGLOBAL | SESSION
Com_show_contributorsnumericGLOBAL | SESSION
Com_show_create_dbnumericGLOBAL | SESSION
Com_show_create_eventnumericGLOBAL | SESSION
Com_show_create_funcnumericGLOBAL | SESSION
Com_show_create_procnumericGLOBAL | SESSION
Com_show_create_tablenumericGLOBAL | SESSION
Com_show_create_triggernumericGLOBAL | SESSION
Com_show_databasesnumericGLOBAL | SESSION
Com_show_engine_logsnumericGLOBAL | SESSION
Com_show_engine_mutexnumericGLOBAL | SESSION
Com_show_engine_statusnumericGLOBAL | SESSION
Com_show_errorsnumericGLOBAL | SESSION
Com_show_eventsnumericGLOBAL | SESSION
Com_show_fieldsnumericGLOBAL | SESSION
Com_show_function_codenumericGLOBAL | SESSION
Com_show_function_statusnumericGLOBAL | SESSION
Com_show_grantsnumericGLOBAL | SESSION
Com_show_innodb_statusnumericGLOBAL | SESSION
Com_show_keysnumericGLOBAL | SESSION
Com_show_logsnumericGLOBAL | SESSION
Com_show_master_statusnumericGLOBAL | SESSION
Com_show_new_masternumericGLOBAL | SESSION
Com_show_open_tablesnumericGLOBAL | SESSION
Com_show_pluginsnumericGLOBAL | SESSION
Com_show_privilegesnumericGLOBAL | SESSION
Com_show_procedure_codenumericGLOBAL | SESSION
Com_show_procedure_statusnumericGLOBAL | SESSION
Com_show_processlistnumericGLOBAL | SESSION
Com_show_profilenumericGLOBAL | SESSION
Com_show_profilesnumericGLOBAL | SESSION
Com_show_relaylog_eventsnumericGLOBAL | SESSION
Com_show_slave_hostsnumericGLOBAL | SESSION
Com_show_slave_statusnumericGLOBAL | SESSION
Com_show_statusnumericGLOBAL | SESSION
Com_show_storage_enginesnumericGLOBAL | SESSION
Com_show_table_statusnumericGLOBAL | SESSION
Com_show_tablesnumericGLOBAL | SESSION
Com_show_triggersnumericGLOBAL | SESSION
Com_show_variablesnumericGLOBAL | SESSION
Com_show_warningsnumericGLOBAL | SESSION
Com_signalnumericGLOBAL | SESSION
Com_slave_startnumericGLOBAL | SESSION
Com_slave_stopnumericGLOBAL | SESSION
Com_stmt_closenumericGLOBAL | SESSION
Com_stmt_executenumericGLOBAL | SESSION
Com_stmt_fetchnumericGLOBAL | SESSION
Com_stmt_preparenumericGLOBAL | SESSION
Com_stmt_repreparenumericGLOBAL | SESSION
Com_stmt_resetnumericGLOBAL | SESSION
Com_stmt_send_long_datanumericGLOBAL | SESSION
Com_truncatenumericGLOBAL | SESSION
Com_uninstall_pluginnumericGLOBAL | SESSION
Com_unlock_tablesnumericGLOBAL | SESSION
Com_updatenumericGLOBAL | SESSION
Com_update_multinumericGLOBAL | SESSION
Com_xa_commitnumericGLOBAL | SESSION
Com_xa_endnumericGLOBAL | SESSION
Com_xa_preparenumericGLOBAL | SESSION
Com_xa_recovernumericGLOBAL | SESSION
Com_xa_rollbacknumericGLOBAL | SESSION
Com_xa_startnumericGLOBAL | SESSION
CompressionnumericSESSION
ConnectionsnumericGLOBAL
Created_tmp_disk_tablesnumericGLOBAL | SESSION
Created_tmp_filesnumericGLOBAL
Created_tmp_tablesnumericGLOBAL | SESSION
Delayed_errorsnumericGLOBAL
Delayed_insert_threadsnumericGLOBAL
Delayed_writesnumericGLOBAL
Flush_commandsnumericGLOBAL
Handler_commitnumericGLOBAL | SESSION
Handler_deletenumericGLOBAL | SESSION
Handler_discovernumericGLOBAL | SESSION
Handler_preparenumericGLOBAL | SESSION
Handler_read_firstnumericGLOBAL | SESSION
Handler_read_keynumericGLOBAL | SESSION
Handler_read_lastnumericGLOBAL | SESSION
Handler_read_nextnumericGLOBAL | SESSION
Handler_read_prevnumericGLOBAL | SESSION
Handler_read_rndnumericGLOBAL | SESSION
Handler_read_rnd_nextnumericGLOBAL | SESSION
Handler_rollbacknumericGLOBAL | SESSION
Handler_savepointnumericGLOBAL | SESSION
Handler_savepoint_rollbacknumericGLOBAL | SESSION
Handler_updatenumericGLOBAL | SESSION
Handler_writenumericGLOBAL | SESSION
Innodb_buffer_pool_pages_datanumericGLOBAL
Innodb_buffer_pool_pages_dirtynumericGLOBAL
Innodb_buffer_pool_pages_flushednumericGLOBAL
Innodb_buffer_pool_pages_freenumericGLOBAL
Innodb_buffer_pool_pages_latchednumericGLOBAL
Innodb_buffer_pool_pages_miscnumericGLOBAL
Innodb_buffer_pool_pages_totalnumericGLOBAL
Innodb_buffer_pool_read_aheadnumericGLOBAL
Innodb_buffer_pool_read_ahead_evictednumericGLOBAL
Innodb_buffer_pool_read_requestsnumericGLOBAL
Innodb_buffer_pool_readsnumericGLOBAL
Innodb_buffer_pool_wait_freenumericGLOBAL
Innodb_buffer_pool_write_requestsnumericGLOBAL
Innodb_data_fsyncsnumericGLOBAL
Innodb_data_pending_fsyncsnumericGLOBAL
Innodb_data_pending_readsnumericGLOBAL
Innodb_data_pending_writesnumericGLOBAL
Innodb_data_readnumericGLOBAL
Innodb_data_readsnumericGLOBAL
Innodb_data_writesnumericGLOBAL
Innodb_data_writtennumericGLOBAL
Innodb_dblwr_pages_writtennumericGLOBAL
Innodb_dblwr_writesnumericGLOBAL
Innodb_have_atomic_builtinsnumericGLOBAL
Innodb_log_waitsnumericGLOBAL
Innodb_log_write_requestsnumericGLOBAL
Innodb_log_writesnumericGLOBAL
Innodb_os_log_fsyncsnumericGLOBAL
Innodb_os_log_pending_fsyncsnumericGLOBAL
Innodb_os_log_pending_writesnumericGLOBAL
Innodb_os_log_writtennumericGLOBAL
Innodb_page_sizenumericGLOBAL
Innodb_pages_creatednumericGLOBAL
Innodb_pages_readnumericGLOBAL
Innodb_pages_writtennumericGLOBAL
Innodb_row_lock_current_waitsnumericGLOBAL
Innodb_row_lock_timenumericGLOBAL
Innodb_row_lock_time_avgnumericGLOBAL
Innodb_row_lock_time_maxnumericGLOBAL
Innodb_row_lock_waitsnumericGLOBAL
Innodb_rows_deletednumericGLOBAL
Innodb_rows_insertednumericGLOBAL
Innodb_rows_readnumericGLOBAL
Innodb_rows_updatednumericGLOBAL
Innodb_truncated_status_writesnumericGLOBAL
Key_blocks_not_flushednumericGLOBAL
Key_blocks_unusednumericGLOBAL
Key_blocks_usednumericGLOBAL
Key_read_requestsnumericGLOBAL
Key_readsnumericGLOBAL
Key_write_requestsnumericGLOBAL
Key_writesnumericGLOBAL
Last_query_costnumericSESSION
Max_used_connectionsnumericGLOBAL
Ndb_conflict_fn_maxnumericGLOBAL
Ndb_conflict_fn_oldnumericGLOBAL
Ndb_number_of_data_nodesnumericGLOBAL
Not_flushed_delayed_rowsnumericGLOBAL
Open_filesnumericGLOBAL
Open_streamsnumericGLOBAL
Open_table_definitionsnumericGLOBAL
Open_tablesnumericGLOBAL | SESSION
Opened_filesnumericGLOBAL
Opened_table_definitionsnumericGLOBAL | SESSION
Opened_tablesnumericGLOBAL | SESSION
Performance_schema_cond_classes_lostnumericGLOBAL
Performance_schema_cond_instances_lostnumericGLOBAL
Performance_schema_file_classes_lostnumericGLOBAL
Performance_schema_file_handles_lostnumericGLOBAL
Performance_schema_file_instances_lostnumericGLOBAL
Performance_schema_locker_lostnumericGLOBAL
Performance_schema_mutex_classes_lostnumericGLOBAL
Performance_schema_mutex_instances_lostnumericGLOBAL
Performance_schema_rwlock_classes_lostnumericGLOBAL
Performance_schema_rwlock_instances_lostnumericGLOBAL
Performance_schema_table_handles_lostnumericGLOBAL
Performance_schema_table_instances_lostnumericGLOBAL
Performance_schema_thread_classes_lostnumericGLOBAL
Performance_schema_thread_instances_lostnumericGLOBAL
Prepared_stmt_countnumericGLOBAL
Qcache_free_blocksnumericGLOBAL
Qcache_free_memorynumericGLOBAL
Qcache_hitsnumericGLOBAL
Qcache_insertsnumericGLOBAL
Qcache_lowmem_prunesnumericGLOBAL
Qcache_not_cachednumericGLOBAL
Qcache_queries_in_cachenumericGLOBAL
Qcache_total_blocksnumericGLOBAL
QueriesnumericGLOBAL | SESSION
QuestionsnumericGLOBAL | SESSION
Rpl_semi_sync_master_clientsnumericGLOBAL
Rpl_semi_sync_master_net_avg_wait_timenumericGLOBAL
Rpl_semi_sync_master_net_wait_timenumericGLOBAL
Rpl_semi_sync_master_net_waitsnumericGLOBAL
Rpl_semi_sync_master_no_timesnumericGLOBAL
Rpl_semi_sync_master_no_txnumericGLOBAL
Rpl_semi_sync_master_statusbooleanGLOBAL
Rpl_semi_sync_master_timefunc_failuresnumericGLOBAL
Rpl_semi_sync_master_tx_avg_wait_timenumericGLOBAL
Rpl_semi_sync_master_tx_wait_timenumericGLOBAL
Rpl_semi_sync_master_tx_waitsnumericGLOBAL
Rpl_semi_sync_master_wait_pos_backtraversenumericGLOBAL
Rpl_semi_sync_master_wait_sessionsnumericGLOBAL
Rpl_semi_sync_master_yes_txnumericGLOBAL
Rpl_semi_sync_slave_statusbooleanGLOBAL
Rpl_statusstringGLOBAL
Select_full_joinnumericGLOBAL | SESSION
Select_full_range_joinnumericGLOBAL | SESSION
Select_rangenumericGLOBAL | SESSION
Select_range_checknumericGLOBAL | SESSION
Select_scannumericGLOBAL | SESSION
Slave_heartbeat_period GLOBAL
Slave_open_temp_tablesnumericGLOBAL
Slave_received_heartbeats GLOBAL
Slave_retried_transactionsnumericGLOBAL
Slave_runningbooleanGLOBAL
Slow_launch_threadsnumericGLOBAL | SESSION
Slow_queriesnumericGLOBAL | SESSION
Sort_merge_passesnumericGLOBAL | SESSION
Sort_rangenumericGLOBAL | SESSION
Sort_rowsnumericGLOBAL | SESSION
Sort_scannumericGLOBAL | SESSION
Ssl_accept_renegotiatesnumericGLOBAL
Ssl_acceptsnumericGLOBAL
Ssl_callback_cache_hitsnumericGLOBAL
Ssl_cipherstringGLOBAL | SESSION
Ssl_cipher_liststringGLOBAL | SESSION
Ssl_client_connectsnumericGLOBAL
Ssl_connect_renegotiatesnumericGLOBAL
Ssl_ctx_verify_depthnumericGLOBAL
Ssl_ctx_verify_modenumericGLOBAL
Ssl_default_timeoutnumericGLOBAL | SESSION
Ssl_finished_acceptsnumericGLOBAL
Ssl_finished_connectsnumericGLOBAL
Ssl_session_cache_hitsnumericGLOBAL
Ssl_session_cache_missesnumericGLOBAL
Ssl_session_cache_modestringGLOBAL
Ssl_session_cache_overflowsnumericGLOBAL
Ssl_session_cache_sizenumericGLOBAL
Ssl_session_cache_timeoutsnumericGLOBAL
Ssl_sessions_reusednumericGLOBAL | SESSION
Ssl_used_session_cache_entriesnumericGLOBAL
Ssl_verify_depthnumericGLOBAL | SESSION
Ssl_verify_modenumericGLOBAL | SESSION
Ssl_versionstringGLOBAL | SESSION
Table_locks_immediatenumericGLOBAL
Table_locks_waitednumericGLOBAL
Tc_log_max_pages_usednumericGLOBAL
Tc_log_page_sizenumericGLOBAL
Tc_log_page_waitsnumericGLOBAL
Threads_cachednumericGLOBAL
Threads_connectednumericGLOBAL
Threads_creatednumericGLOBAL
Threads_runningnumericGLOBAL
UptimenumericGLOBAL
Uptime_since_flush_statusnumericGLOBAL

Many status variables are reset to 0 by the FLUSH STATUS statement.

The status variables have the following meanings. Variables with no version indicated were already present prior to MySQL 5.5. For information regarding their implementation history, see MySQL 5.1 Reference Manual.

  • Aborted_clients

    The number of connections that were aborted because the client died without closing the connection properly. See Section C.5.2.11, “Communication Errors and Aborted Connections”.

  • Aborted_connects

    The number of failed attempts to connect to the MySQL server. See Section C.5.2.11, “Communication Errors and Aborted Connections”.

  • Binlog_cache_disk_use

    The number of transactions that used the binary log cache but that exceeded the value of binlog_cache_size and used a temporary file to store changes from the transaction.

    In MySQL versions 5.5.3 through 5.5.8, this variable also included the number of nontransactional statements that caused the binary log transaction cache to be written to disk. Beginning with MySQL 5.5.9, the number of such nontransactional statements is tracked separately in the Binlog_stmt_cache_disk_use status variable.

  • Binlog_cache_use

    The number of transactions that used the binary log cache.

  • Binlog_stmt_cache_disk_use

    The number of nontransaction statements that used the binary log statement cache but that exceeded the value of binlog_stmt_cache_size and used a temporary file to store those statements.

  • Binlog_stmt_cache_use

    The number of nontransactional statements that used the binary log statement cache.

  • Bytes_received

    The number of bytes received from all clients.

  • Bytes_sent

    The number of bytes sent to all clients.

  • Com_xxx

    The Com_xxx statement counter variables indicate the number of times each xxx statement has been executed. There is one status variable for each type of statement. For example, Com_delete and Com_insert count DELETE and INSERT statements, respectively. However, if a query result is returned from query cache, the server increments the Qcache_hits status variable, not Com_select. See Section 7.9.3.4, “Query Cache Status and Maintenance”.

    All of the Com_stmt_xxx variables are increased even if a prepared statement argument is unknown or an error occurred during execution. In other words, their values correspond to the number of requests issued, not to the number of requests successfully completed.

    The Com_stmt_xxx status variables are as follows:

    • Com_stmt_prepare

    • Com_stmt_execute

    • Com_stmt_fetch

    • Com_stmt_send_long_data

    • Com_stmt_reset

    • Com_stmt_close

    Those variables stand for prepared statement commands. Their names refer to the COM_xxx command set used in the network layer. In other words, their values increase whenever prepared statement API calls such as mysql_stmt_prepare(), mysql_stmt_execute(), and so forth are executed. However, Com_stmt_prepare, Com_stmt_execute and Com_stmt_close also increase for PREPARE, EXECUTE, or DEALLOCATE PREPARE, respectively. Additionally, the values of the older statement counter variables Com_prepare_sql, Com_execute_sql, and Com_dealloc_sql increase for the PREPARE, EXECUTE, and DEALLOCATE PREPARE statements. Com_stmt_fetch stands for the total number of network round-trips issued when fetching from cursors.

    Com_stmt_reprepare indicated the number of times statements were automatically reprepared by the server after metadata changes to tables or views referred to by the statement. A reprepare operation increments Com_stmt_reprepare is incremented, and also Com_stmt_prepare.

  • Compression

    Whether the client connection uses compression in the client/server protocol.

  • Connections

    The number of connection attempts (successful or not) to the MySQL server.

  • Created_tmp_disk_tables

    The number of internal on-disk temporary tables created by the server while executing statements.

    If an internal temporary table is created initially as an in-memory table but becomes too large, MySQL automatically converts it to an on-disk table. The maximum size for in-memory temporary tables is the minimum of the tmp_table_size and max_heap_table_size values. If Created_tmp_disk_tables is large, you may want to increase the tmp_table_size or max_heap_table_size values. value to lessen the likelihood that internal temporary tables in memory will be converted to on-disk tables.

    You can compare the number of internal on-disk temporary tables created to the total number of internal temporary tables created by comparing the values of the Created_tmp_disk_tables and Created_tmp_tables variables.

    See also Section 7.4.3.3, “How MySQL Uses Internal Temporary Tables”.

  • Created_tmp_files

    How many temporary files mysqld has created.

  • Created_tmp_tables

    The number of internal temporary tables created by the server while executing statements.

    You can compare the number of internal on-disk temporary tables created to the total number of internal temporary tables created by comparing the values of the Created_tmp_disk_tables and Created_tmp_tables variables.

    See also Section 7.4.3.3, “How MySQL Uses Internal Temporary Tables”.

    Each invocation of the SHOW STATUS statement uses an internal temporary table and increments the global Created_tmp_tables value.

  • Delayed_errors

    The number of rows written with INSERT DELAYED for which some error occurred (probably duplicate key).

  • Delayed_insert_threads

    The number of INSERT DELAYED handler threads in use.

  • Delayed_writes

    The number of INSERT DELAYED rows written.

  • Flush_commands

    The number of executed FLUSH statements.

  • Handler_commit

    The number of internal COMMIT statements.

  • Handler_delete

    The number of times that rows have been deleted from tables.

  • Handler_prepare

    A counter for the prepare phase of two-phase commit operations.

  • Handler_read_first

    The number of times the first entry in an index was read. If this value is high, it suggests that the server is doing a lot of full index scans; for example, SELECT col1 FROM foo, assuming that col1 is indexed.

  • Handler_read_key

    The number of requests to read a row based on a key. If this value is high, it is a good indication that your tables are properly indexed for your queries.

  • Handler_read_last

    The number of requests to read the last key in an index. With ORDER BY, the server will issue a first-key request followed by several next-key requests, whereas with With ORDER BY DESC, the server will issue a last-key request followed by several previous-key requests. This variable was added in MySQL 5.5.7.

  • Handler_read_next

    The number of requests to read the next row in key order. This value is incremented if you are querying an index column with a range constraint or if you are doing an index scan.

  • Handler_read_prev

    The number of requests to read the previous row in key order. This read method is mainly used to optimize ORDER BY ... DESC.

  • Handler_read_rnd

    The number of requests to read a row based on a fixed position. This value is high if you are doing a lot of queries that require sorting of the result. You probably have a lot of queries that require MySQL to scan entire tables or you have joins that do not use keys properly.

  • Handler_read_rnd_next

    The number of requests to read the next row in the data file. This value is high if you are doing a lot of table scans. Generally this suggests that your tables are not properly indexed or that your queries are not written to take advantage of the indexes you have.

  • Handler_rollback

    The number of requests for a storage engine to perform a rollback operation.

  • Handler_savepoint

    The number of requests for a storage engine to place a savepoint.

  • Handler_savepoint_rollback

    The number of requests for a storage engine to roll back to a savepoint.

  • Handler_update

    The number of requests to update a row in a table.

  • Handler_write

    The number of requests to insert a row in a table.

  • Innodb_buffer_pool_pages_data

    The number of pages containing data (dirty or clean).

  • Innodb_buffer_pool_pages_dirty

    The number of pages currently dirty.

  • Innodb_buffer_pool_pages_flushed

    The number of buffer pool page-flush requests.

  • Innodb_buffer_pool_pages_free

    The number of free pages.

  • Innodb_buffer_pool_pages_latched

    The number of latched pages in InnoDB buffer pool. These are pages currently being read or written or that cannot be flushed or removed for some other reason. Calculation of this variable is expensive, so it is available only when the UNIV_DEBUG system is defined at server build time.

  • Innodb_buffer_pool_pages_misc

    The number of pages that are busy because they have been allocated for administrative overhead such as row locks or the adaptive hash index. This value can also be calculated as Innodb_buffer_pool_pages_totalInnodb_buffer_pool_pages_freeInnodb_buffer_pool_pages_data.

  • Innodb_buffer_pool_pages_total

    The total size of the buffer pool, in pages.

  • Innodb_buffer_pool_read_ahead

    The number of pages read into the InnoDB buffer pool by the read-ahead background thread.

  • Innodb_buffer_pool_read_ahead_evicted

    The number of pages read into the InnoDB buffer pool by the read-ahead background thread that were subsequently evicted without having been accessed by queries.

  • Innodb_buffer_pool_read_requests

    The number of logical read requests InnoDB has done.

  • Innodb_buffer_pool_reads

    The number of logical reads that InnoDB could not satisfy from the buffer pool, and had to read directly from the disk.

  • Innodb_buffer_pool_wait_free

    Normally, writes to the InnoDB buffer pool happen in the background. However, if it is necessary to read or create a page and no clean pages are available, it is also necessary to wait for pages to be flushed first. This counter counts instances of these waits. If the buffer pool size has been set properly, this value should be small.

  • Innodb_buffer_pool_write_requests

    The number writes done to the InnoDB buffer pool.

  • Innodb_data_fsyncs

    The number of fsync() operations so far.

  • Innodb_data_pending_fsyncs

    The current number of pending fsync() operations.

  • Innodb_data_pending_reads

    The current number of pending reads.

  • Innodb_data_pending_writes

    The current number of pending writes.

  • Innodb_data_read

    The amount of data read since the server was started.

  • Innodb_data_reads

    The total number of data reads.

  • Innodb_data_writes

    The total number of data writes.

  • Innodb_data_written

    The amount of data written so far, in bytes.

  • Innodb_dblwr_pages_written

    The number of pages that have been written for doublewrite operations. See Section 13.6.12.1, “InnoDB Disk I/O”.

  • Innodb_dblwr_writes

    The number of doublewrite operations that have been performed. See Section 13.6.12.1, “InnoDB Disk I/O”.

  • Innodb_have_atomic_builtins

    Indicates whether the server was built with atomic instructions.

  • Innodb_log_waits

    The number of times that the log buffer was too small and a wait was required for it to be flushed before continuing.

  • Innodb_log_write_requests

    The number of log write requests.

  • Innodb_log_writes

    The number of physical writes to the log file.

  • Innodb_os_log_fsyncs

    The number of fsync() writes done to the log file.

  • Innodb_os_log_pending_fsyncs

    The number of pending log file fsync() operations.

  • Innodb_os_log_pending_writes

    The number of pending log file writes.

  • Innodb_os_log_written

    The number of bytes written to the log file.

  • Innodb_page_size

    The compiled-in InnoDB page size (default 16KB). Many values are counted in pages; the page size enables them to be easily converted to bytes.

  • Innodb_pages_created

    The number of pages created.

  • Innodb_pages_read

    The number of pages read.

  • Innodb_pages_written

    The number of pages written.

  • Innodb_row_lock_current_waits

    The number of row locks currently being waited for.

  • Innodb_row_lock_time

    The total time spent in acquiring row locks, in milliseconds.

  • Innodb_row_lock_time_avg

    The average time to acquire a row lock, in milliseconds.

  • Innodb_row_lock_time_max

    The maximum time to acquire a row lock, in milliseconds.

  • Innodb_row_lock_waits

    The number of times a row lock had to be waited for.

  • Innodb_rows_deleted

    The number of rows deleted from InnoDB tables.

  • Innodb_rows_inserted

    The number of rows inserted into InnoDB tables.

  • Innodb_rows_read

    The number of rows read from InnoDB tables.

  • Innodb_rows_updated

    The number of rows updated in InnoDB tables.

  • Innodb_truncated_status_writes

    The number of times output from the SHOW ENGINE INNODB STATUS is truncated. Monitoring applications that parse the output from this command can test this value before and after issuing the SHOW ENGINE command, to confirm if the output is complete or not.

  • Key_blocks_not_flushed

    The number of key blocks in the key cache that have changed but have not yet been flushed to disk.

  • Key_blocks_unused

    The number of unused blocks in the key cache. You can use this value to determine how much of the key cache is in use; see the discussion of key_buffer_size in Section 5.1.4, “Server System Variables”.

  • Key_blocks_used

    The number of used blocks in the key cache. This value is a high-water mark that indicates the maximum number of blocks that have ever been in use at one time.

  • Key_read_requests

    The number of requests to read a key block from the cache.

  • Key_reads

    The number of physical reads of a key block from disk. If Key_reads is large, then your key_buffer_size value is probably too small. The cache miss rate can be calculated as Key_reads/Key_read_requests.

  • Key_write_requests

    The number of requests to write a key block to the cache.

  • Key_writes

    The number of physical writes of a key block to disk.

  • Last_query_cost

    The total cost of the last compiled query as computed by the query optimizer. This is useful for comparing the cost of different query plans for the same query. The default value of 0 means that no query has been compiled yet. The default value is 0. Last_query_cost has session scope.

    The Last_query_cost value can be computed accurately only for simple “flat” queries, not complex queries such as those with subqueries or UNION. For the latter, the value is set to 0.

  • Max_used_connections

    The maximum number of connections that have been in use simultaneously since the server started.

  • Not_flushed_delayed_rows

    The number of rows waiting to be written in INSERT DELAYED queues.

  • Open_files

    The number of files that are open. This count includes regular files opened by the server. It does not include other types of files such as sockets or pipes. Also, the count does not include files that storage engines open using their own internal functions rather than asking the server level to do so.

  • Open_streams

    The number of streams that are open (used mainly for logging).

  • Open_table_definitions

    The number of cached .frm files.

  • Open_tables

    The number of tables that are open.

  • Opened_files

    The number of files that have been opened with my_open() (a mysys library function). Parts of the server that open files without using this function do not increment the count.

  • Opened_table_definitions

    The number of .frm files that have been cached.

  • Opened_tables

    The number of tables that have been opened. If Opened_tables is big, your table_open_cache value is probably too small.

  • Prepared_stmt_count

    The current number of prepared statements. (The maximum number of statements is given by the max_prepared_stmt_count system variable.)

  • Qcache_free_blocks

    The number of free memory blocks in the query cache.

  • Qcache_free_memory

    The amount of free memory for the query cache.

  • Qcache_hits

    The number of query cache hits.

  • Qcache_inserts

    The number of queries added to the query cache.

  • Qcache_lowmem_prunes

    The number of queries that were deleted from the query cache because of low memory.

  • Qcache_not_cached

    The number of noncached queries (not cacheable, or not cached due to the query_cache_type setting).

  • Qcache_queries_in_cache

    The number of queries registered in the query cache.

  • Qcache_total_blocks

    The total number of blocks in the query cache.

  • Queries

    The number of statements executed by the server. This variable includes statements executed within stored programs, unlike the Questions variable. It does not count COM_PING or COM_STATISTICS commands.

  • Questions

    The number of statements executed by the server. This includes only statements sent to the server by clients and not statements executed within stored programs, unlike the Queries variable. This variable does not count COM_PING, COM_STATISTICS, COM_STMT_PREPARE, COM_STMT_CLOSE, or COM_STMT_RESET commands.

  • Rpl_semi_sync_master_clients

    The number of semisynchronous slaves.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_net_avg_wait_time

    The average time in microseconds the master waited for a slave reply.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_net_wait_time

    The total time in microseconds the master waited for slave replies.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_net_waits

    The total number of times the master waited for slave replies.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_no_times

    The number of times the master turned off semisynchronous replication.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_no_tx

    The number of commits that were not acknowledged successfully by a slave.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_status

    Whether semisynchronous replication currently is operational on the master. The value is ON if the plugin has been enabled and a commit acknowledgment has occurred. It is OFF if the plugin is not enabled or the master has fallen back to asynchronous replication due to commit acknowledgment timeout.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_timefunc_failures

    The number of times the master failed when calling time functions such as gettimeofday().

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_tx_avg_wait_time

    The average time in microseconds the master waited for each transaction.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_tx_wait_time

    The total time in microseconds the master waited for transactions.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_tx_waits

    The total number of times the master waited for transactions.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_wait_pos_backtraverse

    The total number of times the master waited for an event with binary coordinates lower than events waited for previously. This can occur when the order in which transactions start waiting for a reply is different from the order in which their binary log events are written.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_wait_sessions

    The number of sessions currently waiting for slave replies.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_master_yes_tx

    The number of commits that were acknowledged successfully by a slave.

    This variable is available only if the master-side semisynchronous replication plugin is installed.

  • Rpl_semi_sync_slave_status

    Whether semisynchronous replication currently is operational on the slave. This is ON if the plugin has been enabled and the slave I/O thread is running, OFF otherwise.

    This variable is available only if the slave-side semisynchronous replication plugin is installed.

  • Rpl_status

    The status of fail-safe replication (not implemented). This variable is unused and is removed in MySQL 5.6.

  • Select_full_join

    The number of joins that perform table scans because they do not use indexes. If this value is not 0, you should carefully check the indexes of your tables.

  • Select_full_range_join

    The number of joins that used a range search on a reference table.

  • Select_range

    The number of joins that used ranges on the first table. This is normally not a critical issue even if the value is quite large.

  • Select_range_check

    The number of joins without keys that check for key usage after each row. If this is not 0, you should carefully check the indexes of your tables.

  • Select_scan

    The number of joins that did a full scan of the first table.

  • Slave_heartbeat_period

    Shows the replication heartbeat interval (in seconds) on a replication slave.

  • Slave_open_temp_tables

    The number of temporary tables that the slave SQL thread currently has open. If the value is greater than zero, it is not safe to shut down the slave; see Section 17.4.1.19, “Replication and Temporary Tables”.

  • Slave_received_heartbeats

    This counter increments with each replication heartbeat received by a replication slave since the last time that the slave was restarted or reset, or a CHANGE MASTER TO statement was issued.

  • Slave_retried_transactions

    The total number of times since startup that the replication slave SQL thread has retried transactions.

  • Slave_running

    This is ON if this server is a replication slave that is connected to a replication master, and both the I/O and SQL threads are running; otherwise, it is OFF.

  • Slow_launch_threads

    The number of threads that have taken more than slow_launch_time seconds to create.

  • Slow_queries

    The number of queries that have taken more than long_query_time seconds. See Section 5.2.5, “The Slow Query Log”.

  • Sort_merge_passes

    The number of merge passes that the sort algorithm has had to do. If this value is large, you should consider increasing the value of the sort_buffer_size system variable.

  • Sort_range

    The number of sorts that were done using ranges.

  • Sort_rows

    The number of sorted rows.

  • Sort_scan

    The number of sorts that were done by scanning the table.

  • Ssl_accept_renegotiates

    The number of negotiates needed to establish the connection.

  • Ssl_accepts

    The number of accepted SSL connections.

  • Ssl_callback_cache_hits

    The number of callback cache hits.

  • Ssl_cipher

    The current SSL cipher (empty for non-SSL connections).

  • Ssl_cipher_list

    The list of possible SSL ciphers.

  • Ssl_client_connects

    The number of SSL connection attempts to an SSL-enabled master.

  • Ssl_connect_renegotiates

    The number of negotiates needed to establish the connection to an SSL-enabled master.

  • Ssl_ctx_verify_depth

    The SSL context verification depth (how many certificates in the chain are tested).

  • Ssl_ctx_verify_mode

    The SSL context verification mode.

  • Ssl_default_timeout

    The default SSL timeout.

  • Ssl_finished_accepts

    The number of successful SSL connections to the server.

  • Ssl_finished_connects

    The number of successful slave connections to an SSL-enabled master.

  • Ssl_session_cache_hits

    The number of SSL session cache hits.

  • Ssl_session_cache_misses

    The number of SSL session cache misses.

  • Ssl_session_cache_mode

    The SSL session cache mode.

  • Ssl_session_cache_overflows

    The number of SSL session cache overflows.

  • Ssl_session_cache_size

    The SSL session cache size.

  • Ssl_session_cache_timeouts

    The number of SSL session cache timeouts.

  • Ssl_sessions_reused

    How many SSL connections were reused from the cache.

  • Ssl_used_session_cache_entries

    How many SSL session cache entries were used.

  • Ssl_verify_depth

    The verification depth for replication SSL connections.

  • Ssl_verify_mode

    The verification mode for replication SSL connections.

  • Ssl_version

    The SSL version number.

  • Table_locks_immediate

    The number of times that a request for a table lock could be granted immediately.

  • Table_locks_waited

    The number of times that a request for a table lock could not be granted immediately and a wait was needed. If this is high and you have performance problems, you should first optimize your queries, and then either split your table or tables or use replication.

  • Tc_log_max_pages_used

    For the memory-mapped implementation of the log that is used by mysqld when it acts as the transaction coordinator for recovery of internal XA transactions, this variable indicates the largest number of pages used for the log since the server started. If the product of Tc_log_max_pages_used and Tc_log_page_size is always significantly less than the log size, the size is larger than necessary and can be reduced. (The size is set by the --log-tc-size option. Currently, this variable is unused: It is unneeded for binary log-based recovery, and the memory-mapped recovery log method is not used unless the number of storage engines capable of two-phase commit is greater than one. (InnoDB is the only applicable engine.)

  • Tc_log_page_size

    The page size used for the memory-mapped implementation of the XA recovery log. The default value is determined using getpagesize(). Currently, this variable is unused for the same reasons as described for Tc_log_max_pages_used.

  • Tc_log_page_waits

    For the memory-mapped implementation of the recovery log, this variable increments each time the server was not able to commit a transaction and had to wait for a free page in the log. If this value is large, you might want to increase the log size (with the --log-tc-size option). For binary log-based recovery, this variable increments each time the binary log cannot be closed because there are two-phase commits in progress. (The close operation waits until all such transactions are finished.)

  • Threads_cached

    The number of threads in the thread cache.

  • Threads_connected

    The number of currently open connections.

  • Threads_created

    The number of threads created to handle connections. If Threads_created is big, you may want to increase the thread_cache_size value. The cache miss rate can be calculated as Threads_created/Connections.

  • Threads_running

    The number of threads that are not sleeping.

  • Uptime

    The number of seconds that the server has been up.

  • Uptime_since_flush_status

    The number of seconds since the most recent FLUSH STATUS statement.

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