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4.5.7.3 SHOW STATUS

SHOW STATUS provides server status information (like mysqladmin extended-status). The output resembles that shown here, though the format and numbers probably differ: 

+--------------------------+------------+
| Variable_name            | Value      |
+--------------------------+------------+
| Aborted_clients          | 0          |
| Aborted_connects         | 0          |
| Bytes_received           | 155372598  |
| Bytes_sent               | 1176560426 |
| Connections              | 30023      |
| Created_tmp_disk_tables  | 0          |
| Created_tmp_tables       | 8340       |
| Created_tmp_files        | 60         |
| Delayed_insert_threads   | 0          |
| Delayed_writes           | 0          |
| Delayed_errors           | 0          |
| Flush_commands           | 1          |
| Handler_delete           | 462604     |
| Handler_read_first       | 105881     |
| Handler_read_key         | 27820558   |
| Handler_read_next        | 390681754  |
| Handler_read_prev        | 6022500    |
| Handler_read_rnd         | 30546748   |
| Handler_read_rnd_next    | 246216530  |
| Handler_update           | 16945404   |
| Handler_write            | 60356676   |
| Key_blocks_used          | 14955      |
| Key_read_requests        | 96854827   |
| Key_reads                | 162040     |
| Key_write_requests       | 7589728    |
| Key_writes               | 3813196    |
| Max_used_connections     | 0          |
| Not_flushed_key_blocks   | 0          |
| Not_flushed_delayed_rows | 0          |
| Open_tables              | 1          |
| Open_files               | 2          |
| Open_streams             | 0          |
| Opened_tables            | 44600      |
| Questions                | 2026873    |
| Select_full_join         | 0          |
| Select_full_range_join   | 0          |
| Select_range             | 99646      |
| Select_range_check       | 0          |
| Select_scan              | 30802      |
| Slave_running            | OFF        |
| Slave_open_temp_tables   | 0          |
| Slow_launch_threads      | 0          |
| Slow_queries             | 0          |
| Sort_merge_passes        | 30         |
| Sort_range               | 500        |
| Sort_rows                | 30296250   |
| Sort_scan                | 4650       |
| Table_locks_immediate    | 1920382    |
| Table_locks_waited       | 0          |
| Threads_cached           | 0          |
| Threads_created          | 30022      |
| Threads_connected        | 1          |
| Threads_running          | 1          |
| Uptime                   | 80380      |
+--------------------------+------------+

The status variables listed above have the following meaning:

Variable Meaning
Aborted_clients Number of connections aborted because the client died without closing the connection properly. See section A.2.10 Communication Errors / Aborted Connection.
Aborted_connects Number of tries to connect to the MySQL server that failed. See section A.2.10 Communication Errors / Aborted Connection.
Bytes_received Number of bytes received from all clients.
Bytes_sent Number of bytes sent to all clients.
Com_xxx Number of times each xxx command has been executed.
Connections Number of connection attempts to the MySQL server.
Created_tmp_disk_tables Number of implicit temporary tables on disk created while executing statements.
Created_tmp_tables Number of implicit temporary tables in memory created while executing statements.
Created_tmp_files How many temporary files mysqld has created.
Delayed_insert_threads Number of delayed insert handler threads in use.
Delayed_writes Number of rows written with INSERT DELAYED.
Delayed_errors Number of rows written with INSERT DELAYED for which some error occurred (probably duplicate key).
Flush_commands Number of executed FLUSH commands.
Handler_commit Number of internal COMMIT commands.
Handler_delete Number of times a row was deleted from a table.
Handler_read_first 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 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 Number of requests to read next row in key order. This will be incremented if you are querying an index column with a range constraint. This also will be incremented if you are doing an index scan.
Handler_read_prev Number of requests to read previous row in key order. This is mainly used to optimise ORDER BY ... DESC.
Handler_read_rnd Number of requests to read a row based on a fixed position. This will be high if you are doing a lot of queries that require sorting of the result.
Handler_read_rnd_next Number of requests to read the next row in the datafile. This will be 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 Number of internal ROLLBACK commands.
Handler_update Number of requests to update a row in a table.
Handler_write Number of requests to insert a row in a table.
Key_blocks_used The number of used blocks in the key cache.
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.
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.
Max_used_connections The maximum number of connections in use simultaneously.
Not_flushed_key_blocks Keys blocks in the key cache that has changed but hasn't yet been flushed to disk.
Not_flushed_delayed_rows Number of rows waiting to be written in INSERT DELAY queues.
Open_tables Number of tables that are open.
Open_files Number of files that are open.
Open_streams Number of streams that are open (used mainly for logging).
Opened_tables Number of tables that have been opened.
Rpl_status Status of failsafe replication. (Not yet in use).
Select_full_join Number of joins without keys (If this is not 0, you should carefully check the indexes of your tables).
Select_full_range_join Number of joins where we used a range search on reference table.
Select_range Number of joins where we used ranges on the first table. (It's normally not critical even if this is big.)
Select_scan Number of joins where we did a full scan of the first table.
Select_range_check Number of joins without keys where we check for key usage after each row (If this is not 0, you should carefully check the indexes of your tables).
Questions Number of queries sent to the server.
Slave_open_temp_tables Number of temporary tables currently open by the slave thread
Slave_running Is ON if this is a slave that is connected to a master.
Slow_launch_threads Number of threads that have taken more than slow_launch_time to create.
Slow_queries Number of queries that have taken more than long_query_time seconds. See section 4.9.5 The Slow Query Log.
Sort_merge_passes Number of merges passes the sort algoritm have had to do. If this value is large you should consider increasing sort_buffer.
Sort_range Number of sorts that were done with ranges.
Sort_rows Number of sorted rows.
Sort_scan Number of sorts that were done by scanning the table.
ssl_xxx Variables used by SSL; Not yet implemented.
Table_locks_immediate Number of times a table lock was acquired immediately. Available after 3.23.33.
Table_locks_waited Number of times 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 optimise your queries, and then either split your table(s) or use replication. Available after 3.23.33.
Threads_cached Number of threads in the thread cache.
Threads_connected Number of currently open connections.
Threads_created Number of threads created to handle connections.
Threads_running Number of threads that are not sleeping.
Uptime How many seconds the server has been up.

Some comments about the above:

User Comments

Posted by Sebastian Busch on Wednesday December 18 2002, @5:27pm[Delete] [Edit]

You state for example "if ... is big,
then ...". But: what is big? Relative to
what? It is good that you describe these
conditions, but we should know how these numbers
relate to get an idea of big/large/huge...

Posted by Rich Lafferty on Tuesday January 14 2003, @9:03am[Delete] [Edit]

There are no absolutes for "big". Slashdot's "normal" will be a lot larger than Bob's Trout Forum's "big", for instance.

For the most part, if you're not trying to solve a particular performance problem, you probably don't need to lose sleep over the values; once you have a performance problem to debug, you can use the performance statistics along with slow query logging, no-index query logging, and EXPLAIN to track down the bottleneck queries in your application.

For example, if everything using a table seems to take too long to return, seeing a large Table_locks_waited compared to Table_locks_immediate suggests that waiting for locks is a performance problem; from there you can look at the Handler_read_* figures to see what sort of pathological behavior might be holding locks open, and then compare that to EXPLAINs of the queries in the slow query log to see which queries are causing the problem vs. which are just being slowed down as a result, from which you can start tuning individual queries and indices.

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