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BerkeleyDB-Core-Cxx-Txn.pdf
(1007.21 KB)
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abortresults.html
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apireq.html
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architectrecovery.html
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autocommit.html
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backuprestore.html
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blocking_deadlocks.html
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deadlock.jpg
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enabletxn.html
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envopen.html
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exclusivelock.html
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filemanagement.html
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gettingStarted.css
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hotfailover.html
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index.html
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inmem_txnexample_c.html
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introduction.html
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isolation.html
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lockingsubsystem.html
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logconfig.html
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logfileremoval.html
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maxtxns.html
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moreinfo.html
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multithread-intro.html
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nestedtxn.html
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nodurabletxn.html
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perftune-intro.html
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preface.html
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readblock.jpg
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readmodifywrite.html
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recovery-intro.html
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recovery.html
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reversesplit.html
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rwlocks1-pdf.jpg
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rwlocks1.jpg
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simplelock-pdf.jpg
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simplelock.jpg
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sysfailure.html
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txn_ccursor.html
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txnconcurrency.html
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txncursor.html
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txnexample_c.html
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txnindices.html
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txnnowait.html
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usingtxns.html
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wrapup.html
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writeblock.jpg
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Editing: apireq.html
<?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>Application Requirements</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="introduction.html" title="Chapter 1. Introduction" /> <link rel="prev" href="sysfailure.html" title="A Note on System Failure" /> <link rel="next" href="multithread-intro.html" title="Multi-threaded and Multi-process Applications" /> </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">Application Requirements</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="sysfailure.html">Prev</a> </td> <th width="60%" align="center">Chapter 1. Introduction</th> <td width="20%" align="right"> <a accesskey="n" href="multithread-intro.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="apireq"></a>Application Requirements</h2> </div> </div> </div> <p> In order to use transactions, your application has certain requirements beyond what is required of non-transactional protected applications. They are: </p> <div class="itemizedlist"> <ul type="disc"> <li> <p> Environments. </p> <p> Environments are optional for non-transactional applications, but they are required for transactional applications. </p> <p> Environment usage is described in detail in <a class="xref" href="usingtxns.html" title="Chapter 3. Transaction Basics">Transaction Basics</a>. </p> </li> <li> <p> Transaction subsystem. </p> <p> In order to use transactions, you must explicitly enable the transactional subsystem for your application, and this must be done at the time that your environment is first created. </p> </li> <li> <p> Logging subsystem. </p> <p> The logging subsystem is required for recovery purposes, but its usage also means your application may require a little more administrative effort than it does when logging is not in use. See <a class="xref" href="filemanagement.html" title="Chapter 5. Managing DB Files">Managing DB Files</a> for more information. </p> </li> <li> <p> <span>DbTxn</span> handles. </p> <p> In order to obtain the atomicity guarantee offered by the transactional subsystem (that is, combine multiple operations in a single unit of work), your application must use transaction handles. These handles are obtained from your <span>DbEnv</span> objects. They should normally be short-lived, and their usage is reasonably simple. To complete a transaction and save the work it performed, you call its <code class="methodname">commit()</code> method. To complete a transaction and discard its work, you call its <code class="methodname">abort()</code> method. </p> <p> In addition, it is possible to use auto commit if you want to transactional protect a single write operation. Auto commit allows a transaction to be used without obtaining an explicit transaction handle. See <a class="xref" href="autocommit.html" title="Auto Commit">Auto Commit</a> for information on how to use auto commit. </p> </li> <li> <p> Database open requirements. </p> <p> <span>In addition to using environments and initializing the correct subsystems, your</span> application must transaction protect the database opens<span>, and any secondary index associations,</span> if subsequent operations on the databases are to be transaction protected. The database open and secondary index association are commonly transaction protected using auto commit. </p> </li> <li> <p> Deadlock detection. </p> <p> Typically transactional applications use multiple threads of control when accessing the database. Any time multiple threads are used on a single resource, the potential for lock contention arises. In turn, lock contention can lead to deadlocks. See <a class="xref" href="blocking_deadlocks.html" title="Locks, Blocks, and Deadlocks">Locks, Blocks, and Deadlocks</a> for more information. </p> <p> Therefore, transactional applications must frequently include code for detecting and responding to deadlocks. Note that this requirement is not <span class="emphasis"><em>specific</em></span> to transactions – you can certainly write concurrent non-transactional DB applications. Further, not every transactional application uses concurrency and so not every transactional application must manage deadlocks. Still, deadlock management is so frequently a characteristic of transactional applications that we discuss it in this book. See <a class="xref" href="txnconcurrency.html" title="Chapter 4. Concurrency">Concurrency</a> for more information. </p> </li> </ul> </div> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="sysfailure.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="introduction.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="multithread-intro.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">A Note on System Failure </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> Multi-threaded <span>and Multi-process</span> Applications</td> </tr> </table> </div> </body> </html>
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