Server System Variables The tag to be added to the server identifier in error log output written to  syslog  or the Windows Event Log. This variable is unavailable unless the  log_sink_syseventlog  error log component is installed. See Section 5.4.2.8, “Error Logging to the System Log” . By default, no tag is set, so the server identifier is simply  MySQL  on Windows, and  mysqld  on other platforms. If a tag value of  tag  is specified, it is appended to the server identifier with a leading hyphen, resulting in a  syslog  identifier of  mysqld- tag  (or  MySQL- tag  on Windows). On Windows, to use a tag that does not already exist, the server must be run from an account with Administrator privileges, to permit creation of a registry entry for the tag. Elevated privileges are not required if the tag already exists. The server system time zone. When the server begins executing, it inherits a time zone setting from the machine defaults, possibly modified by the environment of the account used for running the server or the startup script. The value is used to set  system_time_zone . Typically the time zone is specified by the TZ  environment variable. It also can be specified using the  --timezone  option of the  mysqld_safe script. The  system_time_zone  variable differs from  time_zone . Although they might have the same value, the latter variable is used to initialize the time zone for each client that connects. See Section 5.1.15, “MySQL Server Time Zone Support” . The number of table definitions that can be stored in the definition cache. If you use a large number of tables, you can create a large table definition cache to speed up opening of tables. The table definition • table_definition_cache • system_time_zone 897 Default Value empty string System Variable system_time_zone Scope Global Dynamic No SET_VAR  Hint Applies No Type String Command-Line Format --table-definition-cache=# System Variable table_definition_cache Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Integer Default Value -1  (signifies autosizing; do not assign this literal value) Minimum Value 400 Maximum Value 524288