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
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
|
<?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->rep_set_config()</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="rep.html" title="Chapter 10. Replication Methods" />
<link rel="prev" href="repclockskew.html" title="DB_ENV->rep_set_clockskew()" />
<link rel="next" href="repset_limit.html" title="DB_ENV->rep_set_limit()" />
</head>
<body>
<div class="navheader">
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">DB_ENV->rep_set_config()</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="repclockskew.html">Prev</a> </td>
<th width="60%" align="center">Chapter 10.
Replication Methods
</th>
<td width="20%" align="right"> <a accesskey="n" href="repset_limit.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="repconfig"></a>DB_ENV->rep_set_config()</h2>
</div>
</div>
</div>
<pre class="programlisting">#include <db.h>
int
DB_ENV->rep_set_config(DB_ENV *env, u_int32_t which, int onoff); </pre>
<p>
The <code class="methodname">DB_ENV->rep_set_config()</code> method configures the Berkeley DB
replication subsystem.
</p>
<p>
The database environment's replication subsystem may also be
configured using the environment's
<a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a>
file. The syntax of the entry in that file is a single line with
the string "rep_set_config", one or more whitespace characters,
and the method <span class="bold"><strong>which</strong></span> parameter as
a string and optionally one or more whitespace characters, and the
string "on" or "off". If the optional string is omitted, the
default is "on"; for example, "rep_set_config DB_REP_CONF_NOWAIT"
or "rep_set_config DB_REP_CONF_NOWAIT on". Because the
<a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a>
file is read when the database environment is opened, it will silently
overrule configuration done before that time.
</p>
<p>
The <code class="methodname">DB_ENV->rep_set_config()</code> method configures a database
environment, not only operations performed using the specified
<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a> handle.
</p>
<p>
The <code class="methodname">DB_ENV->rep_set_config()</code> method may not be
called to set in-memory replication after the environment is
opened using the
<a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> method.
This method may also not be called to set master leases after the
<a class="xref" href="repstart.html" title="DB_ENV->rep_start()">DB_ENV->rep_start()</a> or
<a class="xref" href="repmgrstart.html" title="DB_ENV->repmgr_start()">DB_ENV->repmgr_start()</a> methods
are called. For all other <span class="bold"><strong>which</strong></span>
parameters, this method may be called at any time during the life
of the application.
</p>
<p>
The <code class="methodname">DB_ENV->rep_set_config()</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="idp53798912"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp53738632"></a>which</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>which</strong></span> parameter must be set to
one of the following values:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p><a id="config_DB_REP_CONF_AUTOINIT"></a>
<code class="literal">DB_REP_CONF_AUTOINIT</code>
</p>
<p>
The replication master will automatically re-initialize outdated
clients. This option is turned on by default.
</p>
</li>
<li>
<p><a id="config_DB_REP_CONF_BULK"></a>
<code class="literal">DB_REP_CONF_BULK</code>
</p>
<p>
The replication master sends groups of records to the clients in a
single network transfer.
</p>
</li>
<li>
<p><a id="config_DB_REP_CONF_DELAYCLIENT"></a>
<code class="literal">DB_REP_CONF_DELAYCLIENT</code>
</p>
<p>
The client should delay synchronizing to a newly declared master.
Clients configured in this way will remain
unsynchronized until the application calls the
<a class="xref" href="repsync.html" title="DB_ENV->rep_sync()">DB_ENV->rep_sync()</a> method.
</p>
</li>
<li>
<p><a id="config_DB_REP_CONF_INMEM"></a>
<code class="literal">DB_REP_CONF_INMEM</code>
</p>
<p>
Store internal replication information in memory only.
</p>
<p>
By default, replication creates files in the environment home directory
to preserve some internal information. If this configuration flag is turned
on, replication only stores this internal information in-memory and cannot
keep persistent state across a site crash or reboot. This results in the
following limitations:
</p>
<div class="itemizedlist">
<ul type="circle">
<li>
<p>
A master site should not reappoint itself master
immediately after crashing or rebooting because the application would incur a
slightly higher risk of client crashes. The former master site should rejoin
the replication group as a client. The application should either hold an
election or appoint a different site to be the next master.
</p>
</li>
<li>
<p>
An application has a slightly higher risk that elections will fail or be
unable to complete. Calling additional elections should eventually yield a
winner.
</p>
</li>
<li>
<p>
An application has a slight risk that the wrong site may win an election,
resulting in the loss of some data. This is consistent with the general loss
of data durability when running in-memory.
</p>
</li>
</ul>
</div>
<p>
This configuration flag can only be turned on before the environment
is opened with the <a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a>
method. Its value cannot be changed while the environment is open.
</p>
</li>
<li>
<p>
<code class="literal">DB_REP_CONF_LEASE</code>
</p>
<p>
Master leases will be used for this site.
</p>
<p>
Configuring this option may result in
<code class="literal">DB_REP_LEASE_EXPIRED</code> error returns
from the <a class="xref" href="dbget.html" title="DB->get()">DB->get()</a> and
<a class="xref" href="dbcget.html" title="DBcursor->get()">DBcursor->get()</a> methods
when attempting to read entries from a database after the site's
master lease has expired.
</p>
<p>
This configuration flag may not be set after the
<a class="xref" href="repmgrstart.html" title="DB_ENV->repmgr_start()">DB_ENV->repmgr_start()</a> method or the
<a class="xref" href="repstart.html" title="DB_ENV->rep_start()">DB_ENV->rep_start()</a>
method is called. All sites in the replication
group should have the same value for this
configuration flag.
</p>
</li>
<li>
<p><a id="config_DB_REP_CONF_NOWAIT"></a>
<code class="literal">DB_REP_CONF_NOWAIT</code>
</p>
<p>
Berkeley DB method calls that would normally block while clients are
in recovery will return errors immediately.
</p>
</li>
<li>
<p><a id="config_DB_REPMGR_CONF_ELECTIONS"></a>
<code class="literal">DB_REPMGR_CONF_ELECTIONS</code>
</p>
<p>
Replication Manager automatically runs elections to
choose a new master when the old master appears to
have become disconnected. This option is turned on
by default.
</p>
<p>
If this option is turned off, the application is
responsible for assigning the new master
explicitly, by calling the
<code class="methodname">DB_ENV->repmgr_start()</code>
method.
</p>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Caution</h3>
<p>
Most Replication Manager
applications should accept the default automatic
behavior. Allowing two sites in a replication
group to act as master simultaneously can lead to
loss of data.
</p>
</div>
<p>
In an application with multiple processes per
database environment, only the main replication
process may change this configuration setting.
</p>
</li>
<li>
<p><a id="config_DB_REPMGR_CONF_2SITE_STRICT"></a>
<code class="literal">DB_REPMGR_CONF_2SITE_STRICT</code>
</p>
<p>
Replication Manager observes the strict "majority" rule in managing
elections, even in a group with only 2 sites. This means the client
in a 2-site group will be unable to take over as master if the
original master fails or becomes disconnected. (See the
<a href="../../programmer_reference/rep_elect.html" class="olink">Elections</a>
section in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em> for more information.)
Both sites in the replication group should have the same value for this
configuration flag.
</p>
</li>
</ul>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp53810928"></a>onoff</h4>
</div>
</div>
</div>
<p>
If the <span class="bold"><strong>onoff</strong></span> parameter
is zero, the configuration flag is turned off.
Otherwise, it is turned on. Most configuration flags are
turned off by default, exceptions are noted above.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp53805640"></a>Errors</h3>
</div>
</div>
</div>
<p>
The <code class="methodname">DB_ENV->rep_set_config()</code> <span>
<span>
method may fail and return one of the following non-zero errors:
</span>
</span>
</p>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp53815168"></a>EINVAL</h4>
</div>
</div>
</div>
<p>
If setting in-memory replication after the database environment is already
opened; if setting master leases after replication is started; if setting
the 2-site strict majority rule for a Base API application;
or if an invalid flag value or parameter was specified.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp53816168"></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="idp53818224"></a>See Also</h3>
</div>
</div>
</div>
<p>
<a class="xref" href="rep.html#replist" title="Replication and Related Methods">Replication 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="repclockskew.html">Prev</a> </td>
<td width="20%" align="center">
<a accesskey="u" href="rep.html">Up</a>
</td>
<td width="40%" align="right"> <a accesskey="n" href="repset_limit.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">DB_ENV->rep_set_clockskew() </td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top"> DB_ENV->rep_set_limit()</td>
</tr>
</table>
</div>
</body>
</html>
|
