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
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
|
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>DB_ENV->close()</title>
<link rel="stylesheet" href="apiReference.css" type="text/css" />
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
<link rel="start" href="index.html" title="Berkeley DB C API Reference" />
<link rel="up" href="env.html" title="Chapter 5. The DB_ENV Handle" />
<link rel="prev" href="envbackup.html" title="DB_ENV->backup()" />
<link rel="next" href="envcreate.html" title="db_env_create" />
</head>
<body>
<div xmlns="" class="navheader">
<div class="libver">
<p>Library Version 12.1.6.1</p>
</div>
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">DB_ENV->close()</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="envbackup.html">Prev</a> </td>
<th width="60%" align="center">Chapter 5.
The DB_ENV Handle
</th>
<td width="20%" align="right"> <a accesskey="n" href="envcreate.html">Next</a></td>
</tr>
</table>
<hr />
</div>
<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="envclose"></a>DB_ENV->close()</h2>
</div>
</div>
</div>
<pre class="programlisting">#include <db.h>
int
DB_ENV->close(DB_ENV *dbenv, u_int32_t flags); </pre>
<p>
The <code class="methodname">DB_ENV->close()</code> method closes the
Berkeley DB environment, freeing any allocated resources and
closing all database handles opened with this environment handle,
as well as closing any underlying subsystems.
</p>
<p>
When you call the <code class="methodname">DB_ENV->close()</code> method,
all open <a class="link" href="db.html" title="Chapter 2. The DB Handle">DB</a> handles and
<a class="link" href="dbc.html" title="Chapter 3. The DBcursor Handle">DBcursor</a> handles are closed
automatically by this function. And, when you close a database
handle, all cursors opened with it are closed automatically.
</p>
<p>
In multiple threads of control, each thread of control opens a
database environment and the database handles within it. When you
close each database handle using the
<code class="methodname">DB_ENV->close()</code> method, by default, the
database is not synchronized and is similar to calling the
<code class="methodname">DB->close(DB_NOSYNC)</code> method. This is to
avoid unncessary database synchronization when there are multiple
environment handles open. To ensure all open database handles are
synchronized when you close the last environment handle, set the
flag parameter value of the <code class="methodname">DB_ENV->close()</code>
method to DB_FORCESYNC. This is similar to calling the
<code class="methodname">DB->close(0)</code> method to close each database
handle.
</p>
<p>
If a database close operation fails, the method returns a non-zero
error value for the first instance of such an error, and continues
to close the rest of the database and environment handles.
</p>
<p>
The <a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a> handle should
not be closed while any other handle that refers to it is not yet
closed; for example, database environment handles must not be closed
while transactions in the environment
have not yet been committed or aborted. Specifically, this includes the
<a class="link" href="txn.html" title="Chapter 12. The DB_TXN Handle">DB_TXN</a>,
<a class="link" href="logc.html" title="The DB_LOGC Handle">DB_LOGC</a> and
<a class="link" href="memp.html" title="Chapter 8. The DB_MPOOLFILE Handle">DB_MPOOLFILE</a> handles.
</p>
<p>
Where the environment was initialized with the
<a class="link" href="envopen.html#envopen_DB_INIT_LOCK">DB_INIT_LOCK</a> flag,
calling <code class="methodname">DB_ENV->close()</code> does not release any locks still held by the
closing process, providing functionality for long-lived locks.
Processes that want to have all their locks released can do so by
issuing the appropriate <a class="xref" href="lockvec.html" title="DB_ENV->lock_vec()">DB_ENV->lock_vec()</a> call.
</p>
<p>
Where the environment was initialized with the
<a class="link" href="envopen.html#envopen_DB_INIT_MPOOL">DB_INIT_MPOOL</a> flag,
calling <code class="methodname">DB_ENV->close()</code> implies calls to
<a class="xref" href="mempfclose.html" title="DB_MPOOLFILE->close()">DB_MPOOLFILE->close()</a> for any
remaining open files in the memory pool that were returned to this
process by calls to <a class="xref" href="mempfopen.html" title="DB_MPOOLFILE->open()">DB_MPOOLFILE->open()</a>. It does
not imply a call to <a class="xref" href="mempfsync.html" title="DB_MPOOLFILE->sync()">DB_MPOOLFILE->sync()</a> for those
files.
</p>
<p>
Where the environment was initialized with the
<a class="link" href="envopen.html#envopen_DB_INIT_TXN">DB_INIT_TXN</a>
flag, calling <code class="methodname">DB_ENV->close()</code> aborts any
unresolved transactions. Applications should not depend on this
behavior for transactions involving Berkeley DB databases; all
such transactions should be explicitly resolved. The problem with
depending on this semantic is that aborting an unresolved
transaction involving database operations requires a database
handle. Because the database handles should have been closed
before calling <code class="methodname">DB_ENV->close()</code>, it will not
be possible to abort the transaction, and recovery will have to be
run on the Berkeley DB environment before further operations are
done.
</p>
<p>
Where log cursors were created using the
<a class="xref" href="logcursor.html" title="DB_ENV->log_cursor()">DB_ENV->log_cursor()</a> method,
calling <code class="methodname">DB_ENV->close()</code> does not imply
closing those cursors.
</p>
<p>
In multithreaded applications, only a single thread may call the
<code class="methodname">DB_ENV->close()</code> method.
</p>
<p>
After <code class="methodname">DB_ENV->close()</code> has been called,
regardless of its return, the Berkeley DB environment handle may
not be accessed again.
</p>
<p>
The <code class="methodname">DB_ENV->close()</code> <span>
<span>
method returns a non-zero error value on failure and 0 on success.
</span>
</span>
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp875232"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp875480"></a>flags</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>flags</strong></span> parameter must be set to 0
or be set to one of the following values:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p><a id="dbenvclose_DB_FORCESYNC"></a>
<code class="literal">DB_FORCESYNC</code>
</p>
<p>
When closing each database handle internally,
synchronize the database. If this flag is not
specified, the database handle is closed without
synchronizing the database.
</p>
</li>
<li>
<p>
<code class="literal">DB_FORCESYNCENV</code>
</p>
<p>
When closing the enviroment, flush memory
mapped environment regions to disk. Specifying
this flag may help prevent loss of updates when
<code class="literal">__db.00*</code> files are on NFS
storage. However, there is a risk that this
flag will significantly slow down this method
call.
</p>
</li>
</ul>
</div>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp922552"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp916464"></a>See Also</h3>
</div>
</div>
</div>
<p>
<a class="xref" href="env.html#envlist" title="Database Environments and Related Methods">Database Environments and Related Methods</a>
</p>
</div>
</div>
<div class="navfooter">
<hr />
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left"><a accesskey="p" href="envbackup.html">Prev</a> </td>
<td width="20%" align="center">
<a accesskey="u" href="env.html">Up</a>
</td>
<td width="40%" align="right"> <a accesskey="n" href="envcreate.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">DB_ENV->backup() </td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top"> db_env_create</td>
</tr>
</table>
</div>
</body>
</html>
|
