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<th colspan="3" align="center">DbSequence::open()</th>
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The DbSequence Handle
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<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="seqopen"></a>DbSequence::open()</h2>
</div>
</div>
</div>
<pre class="programlisting">#include <db_cxx.h>
int
DbSequence::open(DbTxn *txnid, Dbt *key, u_int32_t flags); </pre>
<p>
The <code class="methodname">DbSequence::open()</code> method opens the sequence represented by the
<span class="bold"><strong>key</strong></span>. The key must be compatible with
the underlying database specified in the corresponding call to
<a class="xref" href="seqcreate.html" title="DbSequence">DbSequence</a>.
</p>
<p>
The <code class="methodname">DbSequence::open()</code> <span>
<span>
method either returns a non-zero error value or throws an
exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
</span>
</span>
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp10137000"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp10136352"></a>key</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>key</strong></span> specifies which record in the
database stores the persistent sequence data.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp10124960"></a>flags</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>flags</strong></span> parameter must be set to 0
or by bitwise inclusively <span class="bold"><strong>OR</strong></span>'ing
together one or more of the following values:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<code class="literal">DB_CREATE</code>
</p>
<p>
Create the sequence. If the sequence does not already exist and the
<code class="literal">DB_CREATE</code> flag is not specified, the
<code class="methodname">DbSequence::open()</code> method will fail.
</p>
</li>
<li>
<p>
<code class="literal">DB_EXCL</code>
</p>
<p>
Return an error if the sequence already exists. This flag is only
meaningful when specified with the <code class="literal">DB_CREATE</code> flag.
</p>
</li>
<li>
<p><a id="seqopen_DB_THREAD"></a>
<code class="literal">DB_THREAD</code>
</p>
<p>
Cause the <a class="link" href="seq.html" title="Chapter 12. The DbSequence Handle">DbSequence</a>
handle returned by <code class="methodname">DbSequence::open()</code> to be
<span class="emphasis"><em>free-threaded</em></span>; that is, usable by multiple
threads within a single address space. Note that if multiple threads
create multiple sequences using the same database handle that handle
must have been opened specifying this flag.
</p>
</li>
</ul>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp10141496"></a>txnid</h4>
</div>
</div>
</div>
<p>
If the operation is part of an application-specified transaction, the
<span class="bold"><strong>txnid</strong></span> parameter is a transaction
handle returned from <a class="xref" href="txnbegin.html" title="DbEnv::txn_begin()">DbEnv::txn_begin()</a>; if the
operation is part of a Berkeley DB Concurrent Data Store group, the
<span class="bold"><strong>txnid</strong></span> parameter is a handle returned
from <a class="xref" href="envcdsgroup_begin.html" title="DbEnv::cdsgroup_begin()">DbEnv::cdsgroup_begin()</a>;
otherwise NULL. If no transaction handle is specified, but the
operation occurs in a transactional database, the operation will be
implicitly transaction protected. Transactionally protected operations
on a <a class="link" href="seq.html" title="Chapter 12. The DbSequence Handle">DbSequence</a> handle
require the <a class="link" href="seq.html" title="Chapter 12. The DbSequence Handle">DbSequence</a>
handle itself be transactionally protected during its open if the open
creates the sequence.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp10133224"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="seq.html" title="Chapter 12. The DbSequence Handle">DbSequence</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp10147552"></a>See Also</h3>
</div>
</div>
</div>
<p>
<a class="xref" href="seq.html#seqlist" title="Sequences and Related Methods">Sequences and Related Methods</a>
</p>
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