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
|
<?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>Chapter 6. Summary and Examples</title>
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
<link rel="start" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" />
<link rel="up" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" />
<link rel="prev" href="logconfig.html" title="Configuring the Logging Subsystem" />
<link rel="next" href="txnexample_java.html" title="Base API Transaction Example" />
</head>
<body>
<div xmlns="" class="navheader">
<div class="libver">
<p>Library Version 11.2.5.3</p>
</div>
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">Chapter 6. Summary and Examples</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="logconfig.html">Prev</a> </td>
<th width="60%" align="center"> </th>
<td width="20%" align="right"> <a accesskey="n" href="txnexample_java.html">Next</a></td>
</tr>
</table>
<hr />
</div>
<div class="chapter" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="wrapup"></a>Chapter 6. Summary and Examples</h2>
</div>
</div>
</div>
<div class="toc">
<p>
<b>Table of Contents</b>
</p>
<dl>
<dt>
<span class="sect1">
<a href="wrapup.html#anatomy">Anatomy of a Transactional Application</a>
</span>
</dt>
<dt>
<span class="sect1">
<a href="txnexample_java.html">Base API Transaction Example</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="sect2">
<a href="txnexample_java.html#txnguideexample">TxnGuide.java</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="txnexample_java.html#payloaddata">PayloadData.java</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="txnexample_java.html#dbwriter">DBWriter.java</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="sect1">
<a href="txnexample_dpl.html">DPL Transaction Example</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="sect2">
<a href="txnexample_dpl.html#txnguideexample_dpl">TxnGuide.java</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="txnexample_dpl.html#payloaddataentity">PayloadDataEntity.java</a>
</span>
</dt>
<dt>
<span class="sect2">
<a href="txnexample_dpl.html#storewriter">StoreWriter.java</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="sect1">
<a href="inmem_txnexample_java.html">Base API In-Memory Transaction Example</a>
</span>
</dt>
</dl>
</div>
<p>
Throughout this manual we have presented the concepts and
mechanisms that you need to provide transactional protection for
your application. In this chapter, we summarize these
mechanisms, and we provide a complete example of a multi-threaded
transactional DB application.
</p>
<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="anatomy"></a>Anatomy of a Transactional Application</h2>
</div>
</div>
</div>
<p>
Transactional applications are characterized by performing the
following activities:
</p>
<div class="orderedlist">
<ol type="1">
<li>
<p>
Create your environment handle.
</p>
</li>
<li>
<p>
Open your environment, specifying that the following
subsystems be used:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
Transactional Subsystem (this also initializes the
logging subsystem).
</p>
</li>
<li>
<p>
Memory pool (the in-memory cache).
</p>
</li>
<li>
<p>
Logging subsystem.
</p>
</li>
<li>
<p>
Locking subsystem (if your application is multi-process or multi-threaded).
</p>
</li>
</ul>
</div>
<p>
It is also highly recommended that you run normal recovery
upon first environment open. Normal recovery examines only those logs required
to ensure your database files are consistent relative to the information found in your
log files.
</p>
</li>
<li>
<p>
Optionally spawn off any utility threads that you might need. Utility
threads can be used to run checkpoints periodically, or to
periodically run a deadlock detector if you do not want to
use DB's built-in deadlock detector.
</p>
</li>
<li>
<p>
If you are using the base API, open whatever database handles
that you need. Otherwise, open your store such that it is
configured for transactions.
</p>
</li>
<li>
<p>
Spawn off worker threads. How many of these you need and
how they split their DB workload is entirely up to your
application's requirements. However, any worker threads
that perform write operations will do the following:
</p>
<div class="orderedlist">
<ol type="a">
<li>
<p>
Begin a transaction.
</p>
</li>
<li>
<p>
Perform one or more read and write
operations.
</p>
</li>
<li>
<p>
Commit the transaction if all goes well.
</p>
</li>
<li>
<p>
Abort and retry the operation if a deadlock is
detected.
</p>
</li>
<li>
<p>
Abort the transaction for most other errors.
</p>
</li>
</ol>
</div>
</li>
<li>
<p>
On application shutdown:
</p>
<div class="orderedlist">
<ol type="a">
<li>
<p>
Make sure there are no opened cursors.
</p>
</li>
<li>
<p>
Make sure there are no active transactions. Either
abort or commit all transactions before shutting
down.
</p>
</li>
<li>
<p>
Close your databases or store.
</p>
</li>
<li>
<p>
Close your environment.
</p>
</li>
</ol>
</div>
</li>
</ol>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p>
Robust DB applications should monitor their worker threads to
make sure they have not died unexpectedly. If a thread does
terminate abnormally, you must shutdown all your worker threads
and then run normal recovery (you will have to reopen your
environment to do this). This is the only way to clear any
resources (such as a lock or a mutex) that the abnormally
exiting worker thread might have been holding at the time that
it died.
</p>
<p>
Failure to perform this recovery can cause your
still-functioning worker threads to eventually block forever
while waiting for a lock that will never be released.
</p>
</div>
<p>
In addition to these activities, which are all entirely handled by
code within your application, there are some administrative
activities that you should perform:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
Periodically checkpoint your application. Checkpoints will
reduce the time to run recovery in the event that one is
required. See <a class="xref" href="filemanagement.html#checkpoints" title="Checkpoints">Checkpoints</a>
for details.
</p>
</li>
<li>
<p>
Periodically back up your database and log files. This is
required in order to fully obtain the durability guarantee
made by DB's transaction ACID support. See
<a class="xref" href="backuprestore.html" title="Backup Procedures">Backup Procedures</a>
for more information.
</p>
</li>
<li>
<p>
You may want to maintain a hot failover if 24x7 processing
with rapid restart in the face of a disk hit is important
to you. See <a class="xref" href="hotfailover.html" title="Using Hot Failovers">Using Hot Failovers</a>
for more information.
</p>
</li>
</ul>
</div>
</div>
</div>
<div class="navfooter">
<hr />
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left"><a accesskey="p" href="logconfig.html">Prev</a> </td>
<td width="20%" align="center"> </td>
<td width="40%" align="right"> <a accesskey="n" href="txnexample_java.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">Configuring the Logging Subsystem </td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top"> Base API Transaction Example</td>
</tr>
</table>
</div>
</body>
</html>
|
