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      7.6.6 Version Tokens
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     <span class="section">
      <a href="version-tokens-elements.html">
       7.6.6.1 Version Tokens Elements
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       7.6.6.2 Installing or Uninstalling Version Tokens
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       7.6.6.3 Using Version Tokens
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       7.6.6.4 Version Tokens Reference
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  <p>
   MySQL includes Version Tokens, a feature that enables creation of
      and synchronization around server tokens that applications can use
      to prevent accessing incorrect or out-of-date data.
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   The Version Tokens interface has these characteristics:
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      Version tokens are pairs consisting of a name that serves as a
          key or identifier, plus a value.
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      Version tokens can be locked. An application can use token
          locks to indicate to other cooperating applications that
          tokens are in use and should not be modified.
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      Version token lists are established per server (for example,
          to specify the server assignment or operational state). In
          addition, an application that communicates with a server can
          register its own list of tokens that indicate the state it
          requires the server to be in. An SQL statement sent by the
          application to a server not in the required state produces an
          error. This is a signal to the application that it should seek
          a different server in the required state to receive the SQL
          statement.
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  <p>
   The following sections describe the elements of Version Tokens,
      discuss how to install and use it, and provide reference
      information for its elements.
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