Server Status Variables --extra_cache.key_cache_block_size=2048 shell>  mysqld --key_buffer_size=6M \ --hot_cache.key_buffer_size=2M \ --cold_cache.key_buffer_size=2M mysql>  SET GLOBAL hot_cache.key_buffer_size = 10*1024*1024; mysql>  SET @@GLOBAL.hot_cache.key_buffer_size = 10*1024*1024; mysql>  SELECT @@GLOBAL.hot_cache.key_buffer_size; mysql>  SHOW GLOBAL VARIABLES LIKE ’hot_cache.key_buffer_size’; 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 | +-----------------------------------+------------+ This section provides a description of each status variable. For a status variable summary, see Section 5.1.6, “Server Status Variable Reference” . For information about status variables specific to NDB Cluster, see NDB Cluster Status Variables. Many status variables are reset to 0 by the  FLUSH STATUS  statement. The MySQL 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 13.7.7.37, “SHOW STATUS Statement” ). The optional  GLOBAL  keyword aggregates the values over all connections, and  SESSION  shows the values for the current connection. However, the following statement does not work. The variable is not interpreted as a compound name, but as a simple string for a  LIKE  pattern-matching operation: This is the exception to being able to use structured variable names anywhere a simple variable name may occur. To retrieve the cache size, do this: Structured variable values may be set and retrieved at runtime as well. For example, to set a key cache named  hot_cache  to a size of 10MB, use either of these statements: The following example starts the server with three different key caches having sizes in a 3:1:1 ratio: In this case, the server sets the size of the default key cache to 256KB. (You could also have written --default.key_buffer_size=256K .) In addition, the server creates a second key cache named extra_cache  that has a size of 128KB, with the size of block buffers for caching table index blocks set to 2048 bytes. 5.1.10 Server Status Variables 947