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<chapter>
  <header>
    <copyright>
      <year>2004</year><year>2016</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
 
          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
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    </legalnotice>

    <title>Audit Trail Log</title>
    <prepared></prepared>
    <responsible></responsible>
    <docno></docno>
    <approved></approved>
    <checked></checked>
    <date></date>
    <rev></rev>
    <file>snmp_audit_trail_log.xml</file>
  </header>
  <p>The chapter <em>Audit Trail Log</em> describes the audit trail logging.
    </p>
  <p>Both the agent and the manager can be configured to log 
    incoming and outgoing messages. It uses the Erlang standard log
    mechanism <c>disk_log</c> for logging. The size and location of
    the log files are configurable. A wrap log is used, which means
    that when the log has grown to a maximum size, it starts from the
    beginning of the log, overwriting existing log records.
    </p>
  <p>The log can be either a <c>read</c>, <c>write</c> or a 
    <c>read_write</c>. 
    </p>

  <section>
    <title>Agent Logging</title>
    <p>For the agent, a <c>write</c>, means that all <c>set</c> 
      requests and their responses are stored. No <c>get</c> requests
      or traps are stored in a <c>write</c>. A <c>read_write</c>, 
      all requests, responses and traps are stored.
      </p>
    <p>The log uses a raw data format (basically the BER encoded
      message), in order to minimize the CPU load needed for the log
      mechanism.  This means that the log is not human readable, but
      needs to be formatted off-line before it can be read.  Use the
      function 
      <seealso marker="snmpa#log_to_txt">snmpa:log_to_txt</seealso> 
      for this purpose.
      </p>
  </section>

  <section>
    <title>Manager Logging</title>
    <p>For the manager, a <c>write</c>, means that all  
      requests (<c>set</c> and <c>get</c>) and their responses are stored. 
      No traps are stored in a <c>write</c>. A <c>read_write</c>, 
      all requests, responses and traps are stored.
      </p>
    <p>The log uses a raw data format (basically the BER encoded
      message), in order to minimize the CPU load needed for the log
      mechanism. This means that the log is not human readable, but
      needs to be formatted off-line before it can be read. Use the
      function 
      <seealso marker="snmpm#log_to_txt">snmpm:log_to_txt</seealso> 
      for this purpose.
      </p>
  </section>
</chapter>

