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The DbTxn Handle
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<div class="sect1" lang="en" xml:lang="en">
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<h2 class="title" style="clear: both"><a id="txncommit"></a>DbTxn::commit()</h2>
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<pre class="programlisting">#include <db_cxx.h>
int
DbTxn::commit(u_int32_t flags);</pre>
<p>
The <code class="methodname">DbTxn::commit()</code> method ends the transaction.
</p>
<p>
In the case of nested transactions, if the transaction is a parent
transaction, committing the parent transaction causes all unresolved
children of the parent to be committed. In the case of nested
transactions, if the transaction is a child transaction, its locks are
not released, but are acquired by its parent. Although the commit of
the child transaction will succeed, the actual resolution of the child
transaction is postponed until the parent transaction is committed or
aborted; that is, if its parent transaction commits, it will be
committed; and if its parent transaction aborts, it will be aborted.
</p>
<p>
All cursors opened within the transaction must be closed
before the transaction is committed. If they are not closed,
they will be closed by this function. When the close
operation for a cursor fails, the method returns a non-zero
error value for the first instance of such an error, closes
the rest of the cursors, and then aborts the transaction.
</p>
<p>
After <code class="methodname">DbTxn::commit()</code> has been called, regardless of its return, the
<a class="link" href="txn.html" title="Chapter 13. The DbTxn Handle">DbTxn</a> handle may not be
accessed again. If <code class="methodname">DbTxn::commit()</code> encounters an error, the
transaction and all child transactions of the transaction are aborted.
</p>
<p>
The <code class="methodname">DbTxn::commit()</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>
The errors values that this method returns include the error values of the
<code class="methodname">Dbc::close()</code> method and the following:
</p>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5056136"></a><span>DbDeadlockException or </span>DB_LOCK_DEADLOCK</h4>
</div>
</div>
</div>
<p>
A transactional database environment operation was selected to resolve
a deadlock.
</p>
<p>
<a class="xref" href="dbdeadlock.html" title="DbDeadlockException">DbDeadlockException</a> is thrown if
your Berkeley DB API is configured to throw exceptions.
Otherwise, <code class="literal">DB_LOCK_DEADLOCK</code> is returned.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5035224"></a><span>DbLockNotGrantedException or </span>DB_LOCK_NOTGRANTED</h4>
</div>
</div>
</div>
<p>
A Berkeley DB Concurrent Data Store database environment configured
for lock timeouts was unable to grant a lock in the allowed time.
</p>
<p>
You attempted to open a database handle that is configured
for no waiting exclusive locking, but the exclusive lock could not be
immediately obtained. See
<a class="xref" href="dbset_lk_exclusive.html" title="Db::set_lk_exclusive()">Db::set_lk_exclusive()</a>
for more information.
</p>
<p>
<a class="xref" href="dblocknotgranted.html" title="DbLockNotGrantedException">DbLockNotGrantedException</a> is thrown if
your Berkeley DB API is configured to throw exceptions.
Otherwise, <code class="literal">DB_LOCK_NOTGRANTED</code> is returned.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5065880"></a>DB_REP_LEASE_EXPIRED</h4>
</div>
</div>
</div>
<p>
The operation failed because the site's replication master lease has expired.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5011784"></a>EINVAL</h4>
</div>
</div>
</div>
<p>
If the cursor is already closed; or if an invalid flag value or parameter was specified.
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp5085296"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5085488"></a>flags</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>flags</strong></span> parameter must be set to 0
or one of the following values:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<code class="literal">DB_TXN_NOSYNC</code>
</p>
<p>
Do not synchronously flush the log. This means the transaction will
exhibit the ACI (atomicity, consistency, and isolation) properties,
but not D (durability); that is, database integrity will be
maintained, but it is possible that this transaction may be undone
during recovery.
</p>
<p>
This behavior may be set for a Berkeley DB environment using the
<a class="xref" href="envset_flags.html" title="DbEnv::set_flags()">DbEnv::set_flags()</a>
method or for a single transaction using the
<a class="xref" href="txnbegin.html" title="DbEnv::txn_begin()">DbEnv::txn_begin()</a> method.
Any value specified to this method overrides both of those settings.
</p>
</li>
<li>
<p>
<code class="literal">DB_TXN_SYNC</code>
</p>
<p>
Synchronously flush the log. This means the transaction will exhibit
all of the ACID (atomicity, consistency, isolation, and durability)
properties.
</p>
<p>
This behavior is the default for Berkeley DB environments unless the
<a class="link" href="envset_flags.html#envset_flags_DB_TXN_NOSYNC">DB_TXN_NOSYNC</a>
flag was specified to the
<a class="xref" href="envset_flags.html" title="DbEnv::set_flags()">DbEnv::set_flags()</a> method.
This behavior may also be set for a single transaction using the
<a class="xref" href="txnbegin.html" title="DbEnv::txn_begin()">DbEnv::txn_begin()</a>
method. Any value specified to this method overrides both of those
settings.
</p>
</li>
<li>
<p>
<code class="literal">DB_TXN_WRITE_NOSYNC</code>
</p>
<p>
Write but do not synchronously flush the log on
transaction commit. This means that transactions
exhibit the ACI (atomicity, consistency, and
isolation) properties, but not D (durability); that
is, database integrity will be maintained, but if the
system fails, it is possible some number of the most
recently committed transactions may be undone during
recovery. The number of transactions at risk is
governed by how often the system flushes dirty
buffers to disk and how often the log is
checkpointed.
</p>
<p>
This form of commit protects you against application
crashes, but not against OS crashes. This method
offers less room for the possiblity of data loss than
does <code class="literal">DB_TXN_NOSYNC</code>.
</p>
<p>
This behavior may be set for a Berkeley DB environment using the
<a class="xref" href="envset_flags.html" title="DbEnv::set_flags()">DbEnv::set_flags()</a>
method or for a single transaction using the
<a class="xref" href="txnbegin.html" title="DbEnv::txn_begin()">DbEnv::txn_begin()</a> method.
Any value specified to this method overrides both of those settings.
</p>
</li>
</ul>
</div>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp5089384"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>, <a class="link" href="txn.html" title="Chapter 13. The DbTxn Handle">DbTxn</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp5059072"></a>See Also</h3>
</div>
</div>
</div>
<p>
<a class="xref" href="txn.html#txnlist" title="Transaction Subsystem and Related Methods">Transaction Subsystem and Related Methods</a>
</p>
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