<!--$Id: faq.so,v 10.3 2002/12/10 23:41:42 mjc Exp $--> <!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB Reference Guide: Programmer notes FAQ</title> <meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> <meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> </head> <body bgcolor=white> <table width="100%"><tr valign=top> <td><b><dl><dt>Berkeley DB Reference Guide:<dd>Programmer Notes</dl></b></td> <td align=right><a href="../program/runtime.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../lock/intro.html"><img src="../../images/next.gif" alt="Next"></a> </td></tr></table> <p align=center><b>Programmer notes FAQ</b></p> <ol> <a name="2"><!--meow--></a> <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> </ol> <table width="100%"><tr><td><br></td><td align=right><a href="../program/runtime.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../lock/intro.html"><img src="../../images/next.gif" alt="Next"></a> </td></tr></table> <p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> </body> </html>