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The stack size for each thread. The default is large enough for normal operation. If the thread stack size is too small, it limits the complexity of the SQL statements that the server can handle, the recursion depth of stored procedures, and other memory-consuming actions. 

• time_zone 

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The current time zone. This variable is used to initialize the time zone for each client that connects. By default, the initial value of this is ’SYSTEM’  (which means, “use the value of system_time_zone ” ). The value can be specified explicitly at server startup with the --default-time-zone  option. See Section 5.1.15, “MySQL Server Time Zone Support” . 

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• timestamp 

## Note 

If set to SYSTEM , every MySQL function call that requires a time zone calculation makes a system library call to determine the current system time zone. This call may be protected by a global mutex, resulting in contention. 

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