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<chapter>
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    <copyright>
      <year>1997</year><year>2009</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
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      The contents of this file are subject to the Erlang Public License,
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    <title>Appendix A: Mnesia Error Messages</title>
    <prepared>Claes Wikstr&ouml;m, Hans Nilsson and H&aring;kan Mattsson</prepared>
    <responsible>Bjarne D&auml;cker</responsible>
    <docno></docno>
    <approved>Bjarne D&auml;cker</approved>
    <checked>Bjarne D&auml;cker</checked>
    <date>96-11-20</date>
    <rev>B</rev>
    <file>Mnesia_App_A.xml</file>
  </header>
  <p>Whenever an operation returns an error in Mnesia, a description
    of the error is available. For example, the functions
    <c>mnesia:transaction(Fun)</c>, or <c>mnesia:create_table(N,L)</c>
    may return the tuple <c>{aborted, Reason}</c>, where <c>Reason</c>
    is a term describing the error.  The following function is used to
    retrieve more detailed information about the error:
    </p>
  <list type="bulleted">
    <item><c>mnesia:error_description(Error)</c></item>
  </list>

  <section>
    <title>Errors in Mnesia</title>
    <p>The following is a list of valid errors in Mnesia.</p>
    <list type="bulleted">
      <item><c>badarg</c>.  Bad or invalid argument, possibly bad type.
      </item>
      <item><c>no_transaction</c>. Operation not allowed outside transactions.
      </item>
      <item><c>combine_error</c>. Table options were illegally combined.
      </item>
      <item><c>bad_index</c>. Index already exists, or was out of bounds.
      </item>
      <item><c>already_exists</c>. Schema option to be activated is already on.
      </item>
      <item><c>index_exists</c>. Some operations cannot be performed on tables with an  index.
      </item>
      <item><c>no_exists</c>.; Tried to perform operation on non-existing (non-alive) item.
      </item>
      <item><c>system_limit</c>.; A system limit was exhausted.
      </item>
      <item><c>mnesia_down</c>. A transaction involves records on a
       remote  node which became unavailable before the transaction
       was completed. Record(s) are no longer available elsewhere in
       the network.</item>
      <item><c>not_a_db_node</c>. A node was mentioned which does not exist in the schema.</item>
      <item><c>bad_type</c>.; Bad type specified in argument.</item>
      <item><c>node_not_running</c>. Node is not running.</item>
      <item><c>truncated_binary_file</c>. Truncated binary in file.</item>
      <item><c>active</c>. Some delete operations require that all active records are removed.</item>
      <item><c>illegal</c>. Operation not supported on this record.</item>
    </list>
    <p>The following example illustrates a function which returns an error, and the method to retrieve more detailed error information.
      </p>
    <p>The function <c>mnesia:create_table(bar, [{attributes, 3.14}])</c> will return the tuple <c>{aborted,Reason}</c>, where <c>Reason</c> is the tuple 
      <c>{bad_type,bar,3.14000}</c>. 
      </p>
    <p>The function <c>mnesia:error_description(Reason)</c>, returns the term
      <c>{"Bad type on some provided arguments",bar,3.14000}</c> which is an error
      description suitable
      for display.</p>
  </section>
</chapter>

