Version Tokens +--------------------------------------------+ A client registers the tokens it requires the server to match by setting its  version_tokens_session value. Then, for each subsequent statement sent by the client, the server checks its token list against the client  version_tokens_session  value and produces an error if there is a mismatch: The first  SELECT  succeeds because the client tokens  tok1  and  tok2  are present in the server token list and each token has the same value in the server list. The second  SELECT  fails because, although  tok1 is present in the server token list, it has a different value than specified by the client. At this point, any statement sent by the client fails, unless the server token list changes such that it matches again. Suppose that the management application changes the server token list as follows: Now the client  version_tokens_session  value matches the server token list and the client can once again successfully execute statements: 1109 • version_tokens_session_number mysql>  SET @@SESSION.version_tokens_session = ’tok1=a;tok2=b’; mysql>  SELECT 1; +---+ | 1 | +---+ | 1 | +---+ mysql>  SET @@SESSION.version_tokens_session = ’tok1=b’; mysql>  SELECT 1; ERROR 3136 (42000): Version token mismatch for tok1. Correct value a mysql>  SELECT version_tokens_edit(’tok1=b’); +-------------------------------+ | version_tokens_edit(’tok1=b’) | +-------------------------------+ | 1 version tokens updated. | +-------------------------------+ mysql>  SELECT version_tokens_show(); +-----------------------+ | version_tokens_show() | +-----------------------+ | tok3=c;tok1=b;tok2=b; | +-----------------------+ mysql>  SELECT 1; +---+ | 1 | +---+ | 1 | +---+ This variable is for internal use. Command-Line Format --version-tokens-session-number=# System Variable version_tokens_session_number Scope Global, Session Dynamic No SET_VAR  Hint Applies No Type Integer Default Value 0