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<!--$Id: env_failchk.so,v 10.5 2006/05/26 20:40:50 bostic Exp $-->
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<title>Berkeley DB: DbEnv::failchk</title>
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<h3>DbEnv::failchk</h3>
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<h3><pre>
#include <db_cxx.h>
<p>
int
DbEnv::dbenv_failchk(u_int32_t flags);
</pre></h3>
<hr size=1 noshade>
<h3>Description: DbEnv::failchk</h3>
<p>The DbEnv::failchk 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="../ref/cam/app.html">Architecting Data Store and Concurrent Data Store applications</a>, and
<a href="../ref/transapp/app.html">Architecting Transactional Data Store
applications</a>.</p>
<p>The DbEnv::failchk method is based on the "thread_id" and "is_alive"
functions specified to the <a href="../api_cxx/env_set_thread_id.html">DbEnv::set_thread_id</a> method. Applications
calling the DbEnv::failchk method must have already called the
<a href="../api_cxx/env_set_isalive.html">DbEnv::set_isalive</a> method, on the same <a href="../api_cxx/env_class.html">DbEnv</a>, and must have
configured their database environment using the
<a href="../api_cxx/env_set_thread_count.html">DbEnv::set_thread_count</a> method.</p>
<p>If DbEnv::failchk determines a thread of control exited while
holding database read locks, it will release those locks. If
DbEnv::failchk determines a thread of control exited with an
unresolved transaction, the transaction will be aborted. In either of
these cases, DbEnv::failchk will return 0 and the application may
continue to use the database environment.</p>
<p>In either of these cases, the DbEnv::failchk 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 href="../api_cxx/env_set_msgfile.html">DbEnv::set_msgfile</a> method for more information), or
passed to an application callback function (see the
<a href="../api_cxx/env_set_msgcall.html">DbEnv::set_msgcall</a> method for more information).</p>
<p>If DbEnv::failchk determines a thread of control has exited such
that database environment recovery is required, it will return
<a href="../ref/program/errorret.html#DB_RUNRECOVERY">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="../ref/cam/fail.html">Handling failure in Data Store and
Concurrent Data Store applications</a>, and
<a href="../ref/transapp/fail.html">Handling failure in Transactional
Data Store applications</a>.</p>
<p>The DbEnv::failchk method may not be called before the <a href="../api_cxx/env_open.html">DbEnv::open</a> method has
been called.</p>
<p>The DbEnv::failchk 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.
</p>
<h3>Parameters</h3>
<dl compact>
<dt><b>flags</b><dd>The <b>flags</b> parameter is currently unused, and must be set to 0.
</dl>
<h3>Errors</h3>
<p>The DbEnv::failchk method
may fail and throw
<a href="../api_cxx/except_class.html">DbException</a>,
encapsulating one of the following non-zero errors, or return one of
the following non-zero errors:</p>
<dl compact>
<dt>EINVAL<dd>An
invalid flag value or parameter was specified.
</dl>
<hr size=1 noshade>
<h3>Class</h3>
<a href="../api_cxx/env_class.html">DbEnv</a>
<h3>See Also</h3>
<a href="../api_cxx/env_list.html">Database Environments and Related Methods</a>
</tt>
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