MySQL Reference Manual :: 5.3.4 Server Status Variables

5.3.4. Server Status Variables

The server maintains many status variables that provide information about its operations. You can view these variables and their values by using the SHOW STATUS statement:

mysql> SHOW STATUS;
+--------------------------+------------+
| Variable_name            | Value      |
+--------------------------+------------+
| Aborted_clients          | 0          |
| Aborted_connects         | 0          |
| Bytes_received           | 155372598  |
| Bytes_sent               | 1176560426 |
| Connections              | 30023      |
…

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

The status variables have the following meanings. The Com_xxx statement counter variables were added beginning with MySQL 3.23.47. The Qcache_xxx query cache variables were added beginning with MySQL 4.0.1. Otherwise, variables with no version indicated have been present since at least MySQL 3.22.

Aborted_clients

The number of connections that were aborted because the client died without closing the connection properly. See Section A.2.10, “Communication Errors and Aborted Connections”.
Aborted_connects

The number of tries to connect to the MySQL server that failed. See Section A.2.10, “Communication Errors and Aborted Connections”.
Binlog_cache_disk_use

The number of transactions that used the temporary binary log cache but that exceeded the value of binlog_cache_size and used a temporary file to store statements from the transaction. This variable was added in MySQL 4.1.2.
Binlog_cache_use

The number of transactions that used the temporary binary log cache. This variable was added in MySQL 4.1.2.
Bytes_received

The number of bytes received from all clients. This variable was added in MySQL 3.23.7.
Bytes_sent

The number of bytes sent to all clients. This variable was added in MySQL 3.23.7.
Com_xxx

The Com_xxx statement counter variables were added beginning with MySQL 3.23.47. They 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.

New Com_stmt_xxx status variables have been added in MySQL 4.1.13 or 5.0.8, respectively.
- Com_stmt_prepare
- Com_stmt_execute
- Com_stmt_fetch (not available in versions before 5.0)
- Com_stmt_send_long_data
- Com_stmt_reset
- Com_stmt_close
Those variables stand for prepared statements commands. Their names refer to the COM_xxx command set used in the network layer; in other words: Their values are being increased whenever prepared statements 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 are also increased when one issues the following SQL statements: PREPARE, EXECUTE, or DEALLOCATE respectively. Com_stmt_fetch stands for the total number of network round-trips issued when fetching from cursors.

All of the Com_stmt_xxx variables are increased even if their argument (a prepared statement) 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.
Connections

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

The number of temporary tables on disk created automatically by the server while executing statements. This variable was added in MySQL 3.23.24.
Created_tmp_files

How many temporary files mysqld has created. This variable was added in MySQL 3.23.28.
Created_tmp_tables

The number of in-memory temporary tables created automatically by the server while executing statements. If Created_tmp_disk_tables is big, you may want to increase the tmp_table_size value to cause temporary tables to be memory-based instead of disk-based.
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. This variable was added in MySQL 4.0.2.
Handler_discover

The MySQL server can ask the NDB Cluster storage engine if it knows about a table with a given name. This is called discovery. Handler_discover indicates the number of time tables have been discovered. This variable was added in MySQL 4.1.2.
Handler_delete

The number of times a row was deleted from a table.
Handler_read_first

The number of times the first entry was read from an index. If this 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 is high, it is a good indication that your queries and tables are properly indexed.
Handler_read_next

The number of requests to read the next row in key order. This 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. This variable was added in MySQL 3.23.6.
Handler_read_rnd

The number of requests to read a row based on a fixed position. This 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 whole tables or you have joins that don't use keys properly.
Handler_read_rnd_next

The number of requests to read the next row in the data file. This 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 internal ROLLBACK statements. This variable was added in MySQL 4.0.2.
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). Added in MySQL 5.0.2.
Innodb_buffer_pool_pages_dirty

The number of pages currently dirty. Added in MySQL 5.0.2.
Innodb_buffer_pool_pages_flushed

The number of buffer pool pages that have been requested to be flushed. Added in MySQL 5.0.2.
Innodb_buffer_pool_pages_free

The number of free pages. Added in MySQL 5.0.2.
Innodb_buffer_pool_pages_latched

The number of latched pages in InnoDB buffer pool. These are pages currently being read or written or that can't be flushed or removed for some other reason. Added in MySQL 5.0.2.
Innodb_buffer_pool_pages_misc

The number of pages 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_total - Innodb_buffer_pool_pages_free - Innodb_buffer_pool_pages_data. Added in MySQL 5.0.2.
Innodb_buffer_pool_pages_total

Total size of buffer pool, in pages. Added in MySQL 5.0.2.
Innodb_buffer_pool_read_ahead_rnd

The number of ``random'' read-aheads InnoDB initiated. This happens when a query is to scan a large portion of a table but in random order. Added in MySQL 5.0.2.
Innodb_buffer_pool_read_ahead_seq

The number of sequential read-aheads InnoDB initiated. This happens when InnoDB does a sequential full table scan. Added in MySQL 5.0.2.
Innodb_buffer_pool_read_requests

The number of logical read requests InnoDB has done. Added in MySQL 5.0.2.
Innodb_buffer_pool_reads

The number of logical reads that InnoDB could not satisfy from buffer pool and had to do a single-page read. Added in MySQL 5.0.2.
Innodb_buffer_pool_wait_free

Normally, writes to the InnoDB buffer pool happen in the background. However, if it's necessary to read or create a page and no clean pages are available, it's necessary to wait for pages to be flushed first. This counter counts instances of these waits. If the buffer pool size was set properly, this value should be small. Added in MySQL 5.0.2.
Innodb_buffer_pool_write_requests

The number writes done to the InnoDB buffer pool. Added in MySQL 5.0.2.
Innodb_data_fsyncs

The number of fsync() operations so far. Added in MySQL 5.0.2.
Innodb_data_pending_fsyncs

The current number of pending fsync() operations. Added in MySQL 5.0.2.
Innodb_data_pending_reads

The current number of pending reads. Added in MySQL 5.0.2.
Innodb_data_pending_writes

The current number of pending writes. Added in MySQL 5.0.2.
Innodb_data_read

The amount of data read so far, in bytes. Added in MySQL 5.0.2.
Innodb_data_reads

The total number of data reads. Added in MySQL 5.0.2.
Innodb_data_writes

The total number of data writes. Added in MySQL 5.0.2.
Innodb_data_written

The amount of data written so far, in bytes. Added in MySQL 5.0.2.
Innodb_dblwr_writes , Innodb_dblwr_pages_written

The number of doublewrite writes that have been performed and the number of pages that have been written for this purpose. Added in MySQL 5.0.2.
Innodb_log_waits

The number of waits we had because log buffer was too small and we had to wait for it to be flushed before continuing. Added in MySQL 5.0.2.
Innodb_log_write_requests

The number of log write requests. Added in MySQL 5.0.2.
Innodb_log_writes

The number of physical writes to the log file. Added in MySQL 5.0.2.
Innodb_os_log_fsyncs

The number of fsyncs writes done to the log file. Added in MySQL 5.0.2.
Innodb_os_log_pending_fsyncs

The number of pending log file fsyncs. Added in MySQL 5.0.2.
Innodb_os_log_pending_writes

Pending log file writes. Added in MySQL 5.0.2.
Innodb_os_log_written

The number of bytes written to the log file. Added in MySQL 5.0.2.
Innodb_page_size

The compiled-in InnoDB page size (default 16KB). Many values are counted in pages; the page size allows them to be easily converted to bytes. Added in MySQL 5.0.2.
Innodb_pages_created

The number of pages created. Added in MySQL 5.0.2.
Innodb_pages_read

The number of pages read. Added in MySQL 5.0.2.
Innodb_pages_written

The number of pages written. Added in MySQL 5.0.2.
Innodb_row_lock_current_waits

The number of row locks currently being waited for. Added in MySQL 5.0.3.
Innodb_row_lock_time

The total time spent in acquiring row locks, in milliseconds. Added in MySQL 5.0.3.
Innodb_row_lock_time_avg

The average time to acquire a row lock, in milliseconds. Added in MySQL 5.0.3.
Innodb_row_lock_time_max

The maximum time to acquire a row lock, in milliseconds. Added in MySQL 5.0.3.
Innodb_row_lock_waits

The number of times a row lock had to be waited for. Added in MySQL 5.0.3.
Innodb_rows_deleted

The number of rows deleted from InnoDB tables. Added in MySQL 5.0.2.
Innodb_rows_inserted

The number of rows inserted in InnoDB tables. Added in MySQL 5.0.2.
Innodb_rows_read

The number of rows read from InnoDB tables. Added in MySQL 5.0.2.
Innodb_rows_updated

The number of rows updated in InnoDB tables. Added in MySQL 5.0.2.
Key_blocks_not_flushed

The number of key blocks in the key cache that have changed but haven't yet been flushed to disk. This variable was added in MySQL 4.1.1. It used to be known as Not_flushed_key_blocks.
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 5.3.3, “Server System Variables”. This variable was added in MySQL 4.1.2. Section 5.3.3, “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 big, 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. 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. This variable was added in MySQL 5.0.1, with a default value of -1. In MySQL 5.0.7, the default was changed to 0; also in version 5.0.7, the scope of Last_query_cost was changed to session rather than a global.
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 DELAY queues.
Not_flushed_key_blocks

The old name for Key_blocks_not_flushed before MySQL 4.1.1.
Open_files

The number of files that are open.
Open_streams

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

The number of tables that are open.
Opened_tables

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

The number of free memory blocks in query cache.
Qcache_free_memory

The amount of free memory for query cache.
Qcache_hits

The number of cache hits.
Qcache_inserts

The number of queries added to the cache.
Qcache_lowmem_prunes

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

The number of non-cached queries (not cachable, or not cached due to the query_cache_type setting).
Qcache_queries_in_cache

The number of queries registered in the cache.
Qcache_total_blocks

The total number of blocks in the query cache.
Questions

The number of queries that have been sent to the server.
Rpl_status

The status of failsafe replication (not yet implemented).
Select_full_join

The number of joins that do not use indexes. If this value is not 0, you should carefully check the indexes of your tables. This variable was added in MySQL 3.23.25.
Select_full_range_join

The number of joins that used a range search on a reference table. This variable was added in MySQL 3.23.25.
Select_range

The number of joins that used ranges on the first table. (It's normally not critical even if this is big.) This variable was added in MySQL 3.23.25.
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.) This variable was added in MySQL 3.23.25.
Select_scan

The number of joins that did a full scan of the first table. This variable was added in MySQL 3.23.25.
Slave_open_temp_tables

The number of temporary tables currently open by the slave SQL thread. This variable was added in MySQL 3.23.29.
Slave_running

This is ON if this server is a slave that is connected to a master. This variable was added in MySQL 3.23.16.
Slave_retried_transactions

Total (since startup) number of times the replication slave SQL thread has retried transactions. This variable was added in MySQL 4.1.11 and 5.0.4.
Slow_launch_threads

The number of threads that have taken more than slow_launch_time seconds to create. This variable was added in MySQL 3.23.15.
Slow_queries

The number of queries that have taken more than long_query_time seconds. See Section 5.10.5, “The Slow Query Log”.
Sort_merge_passes

The number of merge passes 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. This variable was added in MySQL 3.23.28.
Sort_range

The number of sorts that were done with ranges. This variable was added in MySQL 3.23.25.
Sort_rows

The number of sorted rows. This variable was added in MySQL 3.23.25.
Sort_scan

The number of sorts that were done by scanning the table. This variable was added in MySQL 3.23.25.
Ssl_xxx

Variables used for SSL connections. These variables were added in MySQL 4.0.0.
Table_locks_immediate

The number of times that a table lock was acquired immediately. This variable was added as of MySQL 3.23.33.
Table_locks_waited

The number of times that a table lock could not be acquired 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. This variable was added as of MySQL 3.23.33.
Threads_cached

The number of threads in the thread cache. This variable was added in MySQL 3.23.17.
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 hit rate can be calculated as Threads_created/Connections. This variable was added in MySQL 3.23.31.
Threads_running

The number of threads that are not sleeping.
Uptime

The number of seconds the server has been up.

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5.3.4. Server Status Variables

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