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<title>Berkeley DB Reference Guide: Programmer notes FAQ</title>
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<td><b><dl><dt>Berkeley DB Reference Guide:<dd>Programmer Notes</dl></b></td>
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<p align=center><b>Programmer notes FAQ</b></p>
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<p><li><b>What priorities should threads/tasks executing Berkeley DB functions
be given?</b>
<p>Tasks executing Berkeley DB functions should have the same, or roughly
equivalent, system priorities. For example, it can be dangerous to give
tasks of control performing checkpoints a lower priority than tasks of
control doing database lookups, and starvation can sometimes result.</p>
<p><li><b>Why isn't the C++ API exception safe?</b>
<p>The Berkeley DB C++ API is a thin wrapper around the C API that maps most
return values to exceptions, and gives the C++ handles the same
lifecycles as their C counterparts. One consequence is that if an
exception occurs while a cursor or transaction handle is open, the
application must explicitly close the cursor or abort the transaction.</p>
<p>Applications can be simplified and bugs avoided by creating wrapper
classes around <a href="../../api_c/dbc_class.html">DBC</a> and <a href="../../api_c/txn_class.html">DB_TXN</a> that call the appropriate
cleanup method in the wrapper's destructor. By creating an instance
of the wrappers on the stack, C++ scoping rules will ensure that the
destructor is called before exception handling unrolls the block that
contains the wrapper object.</p>
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