docs/gsg_txn/C/multithread-intro.html

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   6     <title>Multi-threaded and Multi-process Applications</title>
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  21           <th colspan="3" align="center">Multi-threaded
  22         <span xmlns="http://www.w3.org/1999/xhtml">and Multi-process</span>
  23         Applications</th>
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  27           <th width="60%" align="center">Chapter 1. Introduction</th>
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  37             <h2 class="title" style="clear: both"><a id="multithread-intro"></a>Multi-threaded
  38         <span>and Multi-process</span>
  39         Applications</h2>
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  43       <p>
  44             DB is designed to support multi-threaded  <span>and
  45             multi-process</span> applications, but their usage means
  46             you must pay careful attention to issues of concurrency.
  47             Transactions help your application's concurrency by providing various levels of
  48             isolation for your threads of control. In addition, DB
  49             provides mechanisms that allow you to detect and respond to
  50             deadlocks.
  51         </p>
  52       <p>
  53             <span class="emphasis"><em>Isolation</em></span> means that database modifications made by
  54             one transaction will not normally be seen by readers from another
  55             transaction until the first commits its changes.  Different threads
  56             use different transaction handles, so
  57             this mechanism is normally used to provide isolation between
  58             database operations performed by different threads.
  59         </p>
  60       <p>
  61             Note that DB supports different isolation levels. For example,
  62             you can configure your application to see uncommitted reads, which means
  63             that one transaction can see data that has been modified but not yet
  64             committed by another transaction. Doing this might mean your
  65             transaction reads data "dirtied" by another transaction,
  66             but which subsequently might change before that
  67             other transaction commits its changes.
  68             On the other hand, lowering your isolation
  69             requirements means that your application can experience
  70             improved throughput due to reduced lock contention.
  71         </p>
  72       <p>
  73             For more information on concurrency, on managing isolation
  74             levels, and on deadlock detection, see <a class="xref" href="txnconcurrency.html" title="Chapter 4. Concurrency">Concurrency</a>.
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