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18          <th colspan="3" align="center">Removing Log Files</th>
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20        <tr>
21          <td width="20%" align="left"><a accesskey="p" href="hotfailover.html">Prev</a> </td>
22          <th width="60%" align="center">Chapter 5. Managing DB Files</th>
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30        <div>
31          <div>
32            <h2 class="title" style="clear: both"><a id="logfileremoval"></a>Removing Log Files</h2>
33          </div>
34        </div>
35      </div>
36      <p>
37            By default DB does not delete log files for you. For this reason,
38            DB's log files will eventually grow to consume an
39            unnecessarily large amount of disk space. To guard against
40            this, you should periodically take administrative action to
41            remove log files that are no longer in use by your application.
42        </p>
43      <p>
44            You can remove a log file if all of the following are true:
45        </p>
46      <div class="itemizedlist">
47        <ul type="disc">
48          <li>
49            <p>
50                    the log file is not involved in an active transaction.
51                </p>
52          </li>
53          <li>
54            <p>
55                    a checkpoint has been performed
56                    <span class="emphasis"><em>after</em></span> the log file was
57                    created.
58                </p>
59          </li>
60          <li>
61            <p>
62                    the log file is not the only log file in the
63                    environment.
64                </p>
65          </li>
66          <li>
67            <p>
68                    the log file that you want to remove has already been
69                    included in an offline or hot backup.
70                    Failure to observe this last condition can cause your 
71                    backups to be unusable.
72                </p>
73          </li>
74        </ul>
75      </div>
76      <p>
77            DB provides several mechanisms to remove log files that
78            meet all but the last criteria (DB has no way to know which
79            log files have already been included in a backup). The
80            following mechanisms make it easy to remove unneeded log files,
81            but can result in an unusable backup if the log files are not first 
82            saved to your archive location. All of the following
83            mechanisms automatically delete unneeded log files for you:
84        </p>
85      <div class="itemizedlist">
86        <ul type="disc">
87          <li>
88            <p>
89                    Run the <span class="command"><strong>db_archive</strong></span> command line
90                    utility with the <code class="literal">-d</code> option. 
91                </p>
92          </li>
93          <li>
94            <p>
95                    From within your application, call the
96                        
97                        <span>
98                            <code class="methodname">Environment.removeOldLogFiles()</code>
99                            method.
100                        </span>
101                </p>
102          </li>
103          <li>
104            <p>
105                      
106                        <span>
107                            Specify <code class="literal">true</code> to the
108                            <code class="methodname">EnvironmentConfig.setLogAutoRemove()</code>
109                            method. Note that setting this property affects
110                            all environment handles opened against the
111                            environment; not just the handle used to set
112                            the property.
113                        </span>
114                </p>
115            <p>
116                    Note that unlike the other log removal mechanisms
117                    identified here, this method actually causes log files
118                    to be removed on an on-going basis as they become
119                    unnecessary. This is extremely desirable behavior if
120                    what you want is to use the absolute minimum amount of
121                    disk space possible for your application. This
122                    mechanism <span class="emphasis"><em>will</em></span> leave you with
123                    the log files that are required to run normal recovery.
124                    However, it is highly likely that this mechanism will
125                    prevent you from running catastrophic recovery.
126                </p>
127            <p>
128                    Do NOT use this mechanism if you want to be able to
129                    perform catastrophic recovery, or if you want to be
130                    able to maintain a hot backup.
131                </p>
132          </li>
133        </ul>
134      </div>
135      <p>
136            In order to safely remove log files and still be able to
137            perform catastrophic recovery, use the
138            <span class="command"><strong>db_archive</strong></span> command line utility as follows:
139        </p>
140      <div class="orderedlist">
141        <ol type="1">
142          <li>
143            <p>
144                    Run either a normal or hot backup as described in
145                    <a class="xref" href="backuprestore.html" title="Backup Procedures">Backup Procedures</a>. Make
146                    sure that all of this data is safely stored to your
147                    backup media before continuing.
148                </p>
149          </li>
150          <li>
151            <p>
152                    If you have not already done so, perform a checkpoint.
153                    See <a class="xref" href="filemanagement.html#checkpoints" title="Checkpoints">Checkpoints</a>
154                    for more information.
155                </p>
156          </li>
157          <li>
158            <p>
159                    If you are maintaining a hot backup, perform the hot
160                    backup procedure as described in
161                    <a class="xref" href="hotfailover.html" title="Using Hot Failovers">Using Hot Failovers</a>.
162                </p>
163          </li>
164          <li>
165            <p>
166                    Run the <span class="command"><strong>db_archive</strong></span> command line
167                    utility with the <code class="literal">-d</code> option against
168                    your production environment. 
169                </p>
170          </li>
171          <li>
172            <p>
173                    Run the <span class="command"><strong>db_archive</strong></span> command line
174                    utility with the <code class="literal">-d</code> option against
175                    your failover environment, if you are maintaining one.
176                </p>
177          </li>
178        </ol>
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