1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
|
<!--$Id: faq.so,v 10.3 2002/12/10 23:41:42 mjc Exp $-->
<!--Copyright 1997-2004 by Sleepycat Software, Inc.-->
<!--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><h3><dl><dt>Berkeley DB Reference Guide:<dd>Programmer Notes</dl></h3></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>
<h3 align=center>Programmer notes FAQ</h3>
<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><a href="../../sleepycat/legal.html">Copyright (c) 1996-2004</a> <a href="http://www.sleepycat.com">Sleepycat Software, Inc.</a> - All rights reserved.</font>
</body>
</html>
|