68 lines
4.1 KiB
HTML
68 lines
4.1 KiB
HTML
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Object locks" />
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<meta name="abstract" content="Object locks provide ways to acquire locks on specific system or application objects." />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Object locks</title>
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</head>
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<body id="rzahwobj-objco"><a name="rzahwobj-objco"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Object locks</h1>
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<div><p>Object locks provide ways to acquire locks on specific system or
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application objects.</p>
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<div class="section"><p>In some cases, the system acquires object locks on behalf of actions
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a user takes against certain objects. The system respects and enforces object
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locks for some actions. </p>
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</div>
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<div class="section"><p>You can acquire object locks such that the lock is effective only
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within the thread (thread-scoped) or is effective within the process (process-scoped).
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If two threads in the same process each try to acquire a process-scoped lock
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to a system object, that lock is satisfied for both threads. Neither thread
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prevents the other from acquiring the lock if they are in the same process. </p>
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</div>
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<div class="section"><p>If you are using object locks to protect access to an object from
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two threads within the same process, you should use object locks that are
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scoped to a thread. A thread-scoped object lock never conflicts with an object
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lock scoped to a process that is acquired by the same process.</p>
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</div>
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<div class="section"><p>Object locks allow an application to coordinate the use of different
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locking request types. More than one thread can acquire a shared but thread-scoped
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lock on the same system object. Your application can also acquire different
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types of object locks in a way that is similar to space locks. This allows
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more than one thread to acquire a thread-scoped shared lock on a single target.</p>
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</div>
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<div class="section"><p>Because extra lock types are provided
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by object locks, the concept of an owner is slightly different than it is
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with mutual exclusions (mutexes). There can be multiple owners of a shared,
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thread-scoped lock. If each owner has successfully acquired the shared thread-scoped
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lock, all of the shared locks must be unlocked for a thread to get an exclusive
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thread-scoped object lock.</p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzahwsynco.htm" title="When you create code that is threadsafe but still benefits from sharing data or resources between threads, the most important aspect of programming becomes the ability to synchronize threads.">Synchronization techniques among threads</a></div>
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</div>
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