Sindbad~EG File Manager
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<p>
<span class="bold"><strong>I'm using multiple processes to
access an Berkeley DB database environment; is
there any way to ensure that two processes don't
run transactional recovery at the same time, or
that all processes have exited the database
environment so that recovery can be
run?</strong></span>
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See <a class="xref" href="transapp_fail.html" title="Handling failure in Transactional Data Store applications">Handling failure in Transactional Data Store applications</a> and <a class="xref" href="transapp_app.html" title="Architecting Transactional Data Store applications">Architecting Transactional Data
Store applications</a> for a full
discussion of this topic.
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<span class="bold"><strong>How can I associate application
information with a <a href="../api_reference/C/db.html" class="olink">DB</a> or <a href="../api_reference/C/env.html" class="olink">DB_ENV</a>
handle?</strong></span>
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<p>
In the C API, the <a href="../api_reference/C/db.html" class="olink">DB</a> and <a href="../api_reference/C/env.html" class="olink">DB_ENV</a> structures each
contain an "app_private" field intended to be used to
reference application-specific information. See the
<a href="../api_reference/C/dbcreate.html" class="olink">db_create()</a> and <a href="../api_reference/C/envcreate.html" class="olink">db_env_create()</a> documentation for more
information.
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In the C++ or Java APIs, the easiest way to
associate application-specific data with a handle is
to subclass the <a href="../api_reference/CXX/db.html" class="olink">Db</a> or <a href="../api_reference/CXX/env.html" class="olink">DbEnv</a>, for
example subclassing <a href="../api_reference/CXX/db.html" class="olink">Db</a> to get MyDb.
Objects of type MyDb will still have the Berkeley DB
API methods available on them, and you can put any
extra data or methods you want into the MyDb class. If
you are using "callback" APIs that take <a href="../api_reference/CXX/db.html" class="olink">Db</a>
or <a href="../api_reference/CXX/env.html" class="olink">DbEnv</a> arguments (for example, <a href="../api_reference/CXX/dbset_bt_compare.html" class="olink">Db::set_bt_compare()</a>)
these will always be called with the <a href="../api_reference/CXX/db.html" class="olink">Db</a> or <a href="../api_reference/CXX/env.html" class="olink">DbEnv</a>
objects you create. So if you always use MyDb objects,
you will be able to take the first argument to the
callback function and cast it to a MyDb (in C++, cast
it to (MyDb*)). That will allow you to access your
data members or methods.
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Sindbad File Manager Version 1.0, Coded By Sindbad EG ~ The Terrorists