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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. 

• system_time_zone 

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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” . 

• table_definition_cache 

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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 

