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<h2 class="title" style="clear: both"><a id="xa_faq"></a>XA: Frequently Asked Questions</h2>
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<ol type="1">
<li>
<span class="bold">
<strong>Is it possible to mix XA and non-XA
transactions?</strong>
</span>
<p>
Yes. It is also possible for XA and non-XA
transactions to coexist in the same Berkeley DB
environment. To do this, specify the same environment
to the non-XA <a href="../api_reference/C/envopen.html" class="olink">DB_ENV->open()</a> calls as was specified in the
Tuxedo configuration file.
</p>
</li>
<li>
<span class="bold">
<strong>Does converting an application to
run within XA change any of the already existing C/C++
API calls it does?</strong>
</span>
<p>
When converting an application to run under XA, the
application's Berkeley DB calls are unchanged, with
three exceptions:
</p>
<div class="orderedlist">
<ol type="a">
<li>
The application must specify the
<a href="../api_reference/C/dbcreate.html#dbcreate_DB_XA_CREATE" class="olink">DB_XA_CREATE</a> flag to the <a href="../api_reference/C/dbcreate.html" class="olink">db_create()</a>
function.
</li>
<li>
Unless the application is performing an
operation for a non-XA transaction, the
application should never explicitly call
<a href="../api_reference/C/txncommit.html" class="olink">DB_TXN->commit()</a>, <a href="../api_reference/C/txnabort.html" class="olink">DB_TXN->abort()</a>, and <a href="../api_reference/C/txnbegin.html" class="olink">DB_ENV->txn_begin()</a>, and those
calls should be replaced by calls into the Tuxedo
transaction manager.
</li>
<li>
Unless the application is performing an
operation for a non-XA transaction, the
application should specify a transaction argument
of NULL to Berkeley DB methods taking transaction
arguments (for example, <a href="../api_reference/C/dbput.html" class="olink">DB->put()</a> or
<a href="../api_reference/C/dbcursor.html" class="olink">DB->cursor()</a>).
</li>
</ol>
</div>
<p>
Otherwise, the application should be
unchanged.
</p>
</li>
<li>
<span class="bold">
<strong>How does Berkeley DB recovery
interact with recovery by the Tuxedo transaction
manager?</strong>
</span>
<p>
Recovery is completed in two steps. First, each
resource manager should recover its environment(s).
This can be done via a program that calls <a href="../api_reference/C/envopen.html" class="olink">DB_ENV->open()</a> or
by calling the <a href="../api_reference/C/db_recover.html" class="olink">db_recover</a> utility. If using the
<a href="../api_reference/C/db_recover.html" class="olink">db_recover</a> utility, then the
teoption should be specified so that
the regions that are recovered persist after the
utility exits. Any transactions that were prepared,
but neither completed nor aborted, are restored to
their prepared state so that they may be aborted or
committed via the Tuxedo recovery mechanisms. After
each resource manager has recovered, then Tuxedo
recovery may begin. Tuxedo will interact with each
resource manager via the __db_xa_recover function
which returns the list of prepared, but not yet
completed transactions. It should issue a commit or
abort for each one, and only after having completed
each transaction will normal processing resume.
</p>
<p>
Finally, standard log file archival and catastrophic
recovery procedures should occur independently of XA
operation.
</p>
</li>
<li>
<span class="bold">
<strong>Does Berkeley DB provide
multi-threaded support for XA transactions?</strong>
</span>
<p>
Yes. For information on how to build multi-threaded
servers for XA transactions, see <a class="ulink" href="http://download.oracle.com/docs/cd/E13161_01/tuxedo/docs10gr3/pgc/pgthr.html" target="_top">http://download.oracle.com/docs/cd/E13161_01/tuxedo/docs10gr3/pgc/pgthr.html</a>.
All databases used by servers should be opened
with handles created with the <a href="../api_reference/C/dbcreate.html#dbcreate_DB_XA_CREATE" class="olink">DB_XA_CREATE</a> flag in
the <a href="../api_reference/C/dbcreate.html" class="olink">db_create()</a> method and must be opened in the
tpsvrinit routine. Note that the environment parameter
of the <a href="../api_reference/C/dbcreate.html" class="olink">db_create()</a> method must be assigned NULL. For
more information on the tpsvrinit routine, see <a class="ulink" href="http://download.oracle.com/docs/cd/E13161_01/tuxedo/docs10gr3/pgc/pgthr.html" target="_top">http://download.oracle.com/docs/cd/E13161_01/tuxedo/docs10gr3/pgc/pgthr.html</a>.
</p>
</li>
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<td width="40%" align="right"> <a accesskey="n" href="apprec.html">Next</a></td>
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<td width="40%" align="left" valign="top">Restrictions on XA Transactions </td>
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<a accesskey="h" href="index.html">Home</a>
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<td width="40%" align="right" valign="top"> Chapter 14. Application Specific Logging and
Recovery </td>
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