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<h2 class="title" style="clear: both"><a id="envfailchk"></a>DbEnv::failchk()</h2>
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<pre class="programlisting">#include <db_cxx.h>
int
DbEnv::failchk(u_int32_t flags);</pre>
<p>
The <code class="methodname">DbEnv::failchk()</code> method checks for threads of control (either a
true thread or a process) that have exited while manipulating Berkeley
DB library data structures, while holding a logical database lock, or
with an unresolved transaction (that is, a transaction that was never
aborted or committed). For more information, see
<a href="../../programmer_reference/cam_app.html" class="olink">Architecting Data Store and
Concurrent Data Store applications</a>, and
<a href="../../programmer_reference/transapp_app.html" class="olink">Architecting Transactional
Data Store applications</a>, both in the
<em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
</p>
<p>
The <code class="methodname">DbEnv::failchk()</code> method is based on the <code class="literal">thread_id</code> and
<code class="literal">is_alive</code> functions specified to the
<a class="xref" href="envset_thread_id.html" title="DbEnv::set_thread_id()">DbEnv::set_thread_id()</a>
and
<a class="xref" href="envset_isalive.html" title="DbEnv::set_isalive()">DbEnv::set_isalive()</a>
methods. Applications calling the <code class="methodname">DbEnv::failchk()</code> method must have
already called the <a class="xref" href="envset_isalive.html" title="DbEnv::set_isalive()">DbEnv::set_isalive()</a>
method, on the same <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>, and must have configured
their database environment using the
<a class="xref" href="envset_thread_count.html" title="DbEnv::set_thread_count()">DbEnv::set_thread_count()</a>
method.
</p>
<p>
If <code class="methodname">DbEnv::failchk()</code> determines a thread of control exited while
holding database read locks, it will release those locks. If
<code class="methodname">DbEnv::failchk()</code> determines a thread of control exited with an
unresolved transaction, the transaction will be aborted. In either of
these cases, <code class="methodname">DbEnv::failchk()</code> will return 0 and the application may
continue to use the database environment.
</p>
<p>
In either of these cases, the <code class="methodname">DbEnv::failchk()</code> method will also
report the process and thread IDs associated with any released locks
or aborted transactions. The information is printed to a specified
output channel (see the
<a class="xref" href="envset_msgfile.html" title="DbEnv::set_msgfile()">DbEnv::set_msgfile()</a>
method for more information), or passed to an application callback
function (see the
<a class="xref" href="envset_msgcall.html" title="DbEnv::set_msgcall()">DbEnv::set_msgcall()</a>
method for more information).
</p>
<p>
If <code class="methodname">DbEnv::failchk()</code> determines a thread of control has exited such
that database environment recovery is required, it will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_RUNRECOVERY" class="olink">DB_RUNRECOVERY</a>.
In this case, the application should not continue to use the database
environment. For a further description as to the actions the
application should take when this failure occurs, see
<a href="../../programmer_reference/cam_fail.html" class="olink">Handling failure in Data Store and
Concurrent Data Store applications</a>, and
<a href="../../programmer_reference/transapp_fail.html" class="olink">Handling failure in Transactional Data
Store applications</a>, both in the
<em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
</p>
<p>
In multiprocess applications, it is recommended that the <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle
used to invoke the <code class="methodname">DbEnv::failchk()</code> method not be shared and therefore
not <span class="emphasis"><em>free-threaded</em></span>.
</p>
<p>
The <code class="methodname">DbEnv::failchk()</code> method may not be called by the
application before the <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a>
method is called.
</p>
<p>
The <code class="methodname">DbEnv::failchk()</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="id1664811"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id1664863"></a>flags</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>flags</strong></span> parameter is currently
unused, and must be set to 0.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id1665013"></a>Errors</h3>
</div>
</div>
</div>
<p>
The <code class="methodname">DbEnv::failchk()</code> <span>
<span>
method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
exception, encapsulating one of the following non-zero errors, or return one
of the following non-zero errors:
</span>
</span>
</p>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id1664924"></a>EINVAL</h4>
</div>
</div>
</div>
<p>
An invalid flag value or parameter was specified.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id1664774"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="id1664920"></a>See Also</h3>
</div>
</div>
</div>
<p>
<a class="xref" href="env.html#envlist" title="Database Environments and Related Methods">Database Environments and Related Methods</a>
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