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<title>LockConflictException (Oracle - Berkeley DB Java Edition API)</title>
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<div class="aboutLanguage"><b>Berkeley DB Java Edition</b><br><font size=\"-1\"> version 7.5.11</font>
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<h2 title="Class LockConflictException" class="title">Class LockConflictException</h2>
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<li><a href="../../../com/sleepycat/je/DatabaseException.html" title="class in com.sleepycat.je">com.sleepycat.je.DatabaseException</a></li>
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<dt>Direct Known Subclasses:</dt>
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<dd><a href="../../../com/sleepycat/je/DeadlockException.html" title="class in com.sleepycat.je">DeadlockException</a>, <a href="../../../com/sleepycat/je/LockNotAvailableException.html" title="class in com.sleepycat.je">LockNotAvailableException</a>, <a href="../../../com/sleepycat/je/rep/LockPreemptedException.html" title="class in com.sleepycat.je.rep">LockPreemptedException</a>, <a href="../../../com/sleepycat/je/LockTimeoutException.html" title="class in com.sleepycat.je">LockTimeoutException</a>, <a href="../../../com/sleepycat/je/TransactionTimeoutException.html" title="class in com.sleepycat.je">TransactionTimeoutException</a></dd>
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</dl>
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<hr>
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<br>
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<pre>public abstract class <span class="typeNameLabel">LockConflictException</span>
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extends <a href="../../../com/sleepycat/je/OperationFailureException.html" title="class in com.sleepycat.je">OperationFailureException</a></pre>
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<div class="block">The common base class for all exceptions that result from record lock
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conflicts during read and write operations.
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<p>This exception normally indicates that a transaction may be retried.
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Catching this exception, rather than its subclasses, is convenient and
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recommended for handling lock conflicts and performing transaction retries
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in a general purpose manner. See below for information on performing
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transaction retries.</p>
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<p>The exception carries two arrays of transaction ids, one of the owners and
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the other of the waiters, at the time of the lock conflict. This
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information may be used along with the <a href="../../../com/sleepycat/je/Transaction.html#getId--"><code>Transaction
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ID</code></a> for diagnosing locking problems. See <a href="../../../com/sleepycat/je/LockConflictException.html#getOwnerTxnIds--"><code>getOwnerTxnIds()</code></a> and <a href="../../../com/sleepycat/je/LockConflictException.html#getWaiterTxnIds--"><code>getWaiterTxnIds()</code></a>.</p>
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<p>The <a href="../../../com/sleepycat/je/Transaction.html" title="class in com.sleepycat.je"><code>Transaction</code></a> handle is invalidated as a result of this
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exception.</p>
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<a name="retries"><h3>Performing Transaction Retries</h3></a>
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<p>If a lock conflict occurs during a transaction, the transaction may be
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retried by performing the following steps. Some applications may also wish
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to sleep for a short interval before retrying, to give other concurrent
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transactions a chance to finish and release their locks.</p>
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<ol>
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<li>Close all cursors opened under the transaction.</li>
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<li>Abort the transaction.</li>
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<li>Begin a new transaction and repeat the operations.</li>
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</ol>
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<p>To handle <a href="../../../com/sleepycat/je/LockConflictException.html" title="class in com.sleepycat.je"><code>LockConflictException</code></a> reliably for all types of JE
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applications including JE-HA applications, it is important to handle it when
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it is thrown by all <a href="../../../com/sleepycat/je/Database.html" title="class in com.sleepycat.je"><code>Database</code></a> and <a href="../../../com/sleepycat/je/Cursor.html" title="class in com.sleepycat.je"><code>Cursor</code></a> read and write
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operations.</p>
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<p>The following example code illustrates the recommended approach. Note
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that the <code>Environment.beginTransaction</code> and <code>Transaction.commit</code>
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calls are intentially inside the <code>try</code> block. When using JE-HA, this
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will make it easy to add a <code>catch</code> for other exceptions that can be
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resolved by retrying the transaction, such as consistency exceptions.</p>
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<pre class="code">
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void doTransaction(final Environment env,
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final Database db1,
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final Database db2,
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final int maxTries)
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throws DatabaseException {
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boolean success = false;
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long sleepMillis = 0;
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for (int i = 0; i < maxTries; i++) {
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// Sleep before retrying.
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if (sleepMillis != 0) {
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Thread.sleep(sleepMillis);
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sleepMillis = 0;
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}
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Transaction txn = null;
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try {
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txn = env.beginTransaction(null, null);
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final Cursor cursor1 = db1.openCursor(txn, null);
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try {
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final Cursor cursor2 = db2.openCursor(txn, null);
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try {
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// INSERT APP-SPECIFIC CODE HERE:
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// Perform read and write operations.
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} finally {
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cursor2.close();
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}
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} finally {
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cursor1.close();
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}
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txn.commit();
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success = true;
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return;
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} catch (LockConflictException e) {
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sleepMillis = LOCK_CONFLICT_RETRY_SEC * 1000;
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continue;
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} finally {
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if (!success) {
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if (txn != null) {
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txn.abort();
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}
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}
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}
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}
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// INSERT APP-SPECIFIC CODE HERE:
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// Transaction failed, despite retries.
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// Take some app-specific course of action.
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}</pre>
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<p>For more information on transactions and lock conflicts, see <a
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href="../../../../TransactionGettingStarted/index.html"
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target="_top">Writing Transactional Applications</a>.</p></div>
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<dl>
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<dt><span class="simpleTagLabel">Since:</span></dt>
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<dd>4.0</dd>
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<dt><span class="seeLabel">See Also:</span></dt>
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<dd><a href="../../../serialized-form.html#com.sleepycat.je.LockConflictException">Serialized Form</a></dd>
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</dl>
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<h3>Method Summary</h3>
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<table class="memberSummary" border="0" cellpadding="3" cellspacing="0" summary="Method Summary table, listing methods, and an explanation">
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<caption><span id="t0" class="activeTableTab"><span>All Methods</span><span class="tabEnd"> </span></span><span id="t2" class="tableTab"><span><a href="javascript:show(2);">Instance Methods</a></span><span class="tabEnd"> </span></span><span id="t4" class="tableTab"><span><a href="javascript:show(8);">Concrete Methods</a></span><span class="tabEnd"> </span></span></caption>
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<th class="colFirst" scope="col">Modifier and Type</th>
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<tr id="i0" class="altColor">
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<td class="colFirst"><code>long[]</code></td>
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<td class="colLast"><code><span class="memberNameLink"><a href="../../../com/sleepycat/je/LockConflictException.html#getOwnerTxnIds--">getOwnerTxnIds</a></span>()</code>
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<div class="block">Returns an array of longs containing transaction ids of owners at the
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the time of the timeout.</div>
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</td>
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</tr>
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<tr id="i1" class="rowColor">
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<td class="colFirst"><code>long[]</code></td>
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<td class="colLast"><code><span class="memberNameLink"><a href="../../../com/sleepycat/je/LockConflictException.html#getWaiterTxnIds--">getWaiterTxnIds</a></span>()</code>
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<div class="block">Returns an array of longs containing transaction ids of waiters at the
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the time of the timeout.</div>
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</td>
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</tr>
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</table>
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<h3>Methods inherited from class com.sleepycat.je.<a href="../../../com/sleepycat/je/DatabaseException.html" title="class in com.sleepycat.je">DatabaseException</a></h3>
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<code><a href="../../../com/sleepycat/je/DatabaseException.html#getMessage--">getMessage</a></code></li>
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<h3>Methods inherited from class java.lang.Throwable</h3>
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<code>addSuppressed, fillInStackTrace, getCause, getLocalizedMessage, getStackTrace, getSuppressed, initCause, printStackTrace, printStackTrace, printStackTrace, setStackTrace, toString</code></li>
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<h3>Methods inherited from class java.lang.Object</h3>
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<code>clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait</code></li>
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</ul>
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<div class="details">
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<!-- ============ METHOD DETAIL ========== -->
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<li class="blockList"><a name="method.detail">
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<!-- -->
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</a>
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<h3>Method Detail</h3>
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<a name="getOwnerTxnIds--">
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<!-- -->
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</a>
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<ul class="blockList">
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<li class="blockList">
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<h4>getOwnerTxnIds</h4>
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<pre>public long[] getOwnerTxnIds()</pre>
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<div class="block">Returns an array of longs containing transaction ids of owners at the
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the time of the timeout.</div>
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||
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<dl>
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||
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<dt><span class="returnLabel">Returns:</span></dt>
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<dd>an array of longs containing transaction ids of owners at the
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the time of the timeout.</dd>
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</dl>
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</li>
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</ul>
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<a name="getWaiterTxnIds--">
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<!-- -->
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</a>
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<ul class="blockListLast">
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<li class="blockList">
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<h4>getWaiterTxnIds</h4>
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<pre>public long[] getWaiterTxnIds()</pre>
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<div class="block">Returns an array of longs containing transaction ids of waiters at the
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the time of the timeout.</div>
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<dl>
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||
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<dt><span class="returnLabel">Returns:</span></dt>
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||
|
<dd>an array of longs containing transaction ids of waiters at the
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the time of the timeout.</dd>
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</dl>
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</li>
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</ul>
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</li>
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</ul>
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</li>
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</ul>
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