95 lines
5.8 KiB
HTML
95 lines
5.8 KiB
HTML
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<meta name="DC.Title" content="Locked objects" />
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<title>Locked objects</title>
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<body id="rzakslockedobjstructure"><a name="rzakslockedobjstructure"><!-- --></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">Locked objects</h1>
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<div><p>Jobs and threads use objects to process work.</p>
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<p>Because more than one piece of work is processing at a time, a lock is
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put on an object so that data integrity is retained. <dfn class="term">Locked objects</dfn> are
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system objects used by jobs and threads to process work. After the job or
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thread is finished running, the object is unlocked and ready to be used to
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process more work. Depending on the lock request type used, locking an object
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permits only one user to use an object at a time. For example, if two or more
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users tried to change an object at the same time, the changes to the object
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by the second user is locked out until the first user finished updating the
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object. With the use of lock holders, a user can see what currently has a
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lock or is currently waiting on a lock for an object.</p>
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<p><dfn class="term">Scope</dfn> specifies whether the lock is associated with a job,
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a thread, or a lock space. Scope also defines how long the lock will be available
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and what lock request type and conflict rules the object has on it.</p>
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<p><dfn class="term">Lock request types</dfn> are different levels of access that a job,
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thread or lock space can have to an object that is locked. For example, a
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lock exclusive, no read lock type is used if an object is being changed or
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deleted on the system. This lock request type does not allow anyone to use
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the object, nor does it allow anyone to read the object.</p>
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<p>The different lock request types are:</p>
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<dl><dt class="dlterm">Exclusive - No read</dt>
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<dd>The object is reserved for exclusive use. However, if the object is locked
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by any lock request type, you cannot obtain exclusive use of the object. This
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lock state is appropriate when a user does not want any other user to have
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access to the object until the function being performed is complete.</dd>
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</dl>
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<dl><dt class="dlterm">Exclusive-Read</dt>
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<dd>The object can only be shared with the shared-read lock request type.
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This lock is appropriate when a user wants to prevent other users from performing
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any operation other than a read.</dd>
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</dl>
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<dl><dt class="dlterm">Shared-Update</dt>
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<dd>The object can be shared with either the shared-read or shared-update
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lock request type. That is, another user can request either a shared-read
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lock state or a shared-update lock state for the same object. This lock state
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is appropriate when a user intends to change an object but wants to allow
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other users to read or change the same object.</dd>
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</dl>
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<dl><dt class="dlterm">Shared-No update</dt>
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<dd>The object can be shared with only share - no update, and shared-read
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lock request types. This lock state is appropriate when a user does not intend
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to change an object but wants to ensure that no other user changes the object.</dd>
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</dl>
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<dl><dt class="dlterm">Shared-Read</dt>
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<dd>The object can be shared with all lock requests other than exclusive -
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no read. That is, another user can request an exclusive-read, shared-update,
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shared-read, or shared-no update lock state.</dd>
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</dl>
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<p>The <dfn class="term">lock status</dfn> tells the state of the lock request. The different
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lock statuses are:</p>
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<ul class="simple"><li><strong>Held</strong>: The lock request has been fulfilled and the job, thread
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or lock space is holding the lock.</li>
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<li><strong>Waiting</strong>: The job or thread is waiting to obtain the lock.</li>
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<li><strong>Requested</strong>: The job or thread has requested the lock.</li>
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</ul>
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<p><dfn class="term">Lock holders</dfn> are the jobs, threads and lock spaces that are
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currently holding a lock or are waiting for a lock on a specific locked object.</p>
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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="rzaksjobcharacter.htm" title="Work management provides a way for you to control the work done on your system through a job's attributes. However, before you can control the various aspects of a job, you need to understand the different characteristics of a job.">Job characteristics</a></div>
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</div>
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</div>
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