99 lines
7.5 KiB
HTML
99 lines
7.5 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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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="concept" />
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<meta name="DC.Title" content="Time adjustment" />
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<meta name="abstract" content="Learn how a time maintenance application automatically adjusts system time and how you can manually make time adjustments to the system time. Also, learn how a time adjustment is different from manually setting the time of day system value and why a time adjustment is the preferred method when changing the system time." />
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<meta name="description" content="Learn how a time maintenance application automatically adjusts system time and how you can manually make time adjustments to the system time. Also, learn how a time adjustment is different from manually setting the time of day system value and why a time adjustment is the preferred method when changing the system time." />
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<meta name="DC.Relation" scheme="URI" content="rzatitimemainapp.htm" />
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<meta name="DC.Relation" scheme="URI" content="../rzakz/rzakzqtime.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzati3minuteadj.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzatiadjustsystime.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzatitimeoff.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Identifier" content="rzatitimeadj" />
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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>Time adjustment</title>
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</head>
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<body id="rzatitimeadj"><a name="rzatitimeadj"><!-- --></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">Time adjustment</h1>
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<div><p>Learn how a time maintenance application automatically adjusts
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system time and how you can manually make time adjustments to the system time.
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Also, learn how a time adjustment is different from manually setting the time
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of day system value and why a time adjustment is the preferred method when
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changing the system time.</p>
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<p>The time adjustment function of iSeries™ Navigator allows you to make
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adjustments to the system time or to use a time maintenance application to
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make adjustments to the system time automatically. Time adjustments are preferred
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over manually setting the time of day system value because a time adjustment
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speeds up or slows down time in small increments rather than making a single,
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instantaneous time change.</p>
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<p>Prior to time adjustments, you can manually change the system time using
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the time of day system value. For example, if you wanted to set the system
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time backward three minutes, you would manually change the time of day system
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value from 3:00:00 (HH:MM:SS) to 2:57:00. By doing this, the system time from
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2:57:00 to 3:00:00 is repeated. This can cause problems for applications recording
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time.</p>
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<p>To avoid these types of problems, you can use a time adjustment to change
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the system time and time will not be skipped or repeated. Adjusting the clock
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means to incrementally speed up or slow down the clock so that time is gradually
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adjusted to the desired time value. Adjusting does not cause large jumps in
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time that can be experienced with setting the clock with the time of day system
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value. However, adjusting does take time to complete because it is not a single,
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instantaneous change to the clock. For example, adjusting the clock by 1 second
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can take 10 seconds of real time to complete.</p>
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<p>The following figure shows the difference between manually setting the
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time of day system value and using the time adjustment function. The lines
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represent the progression forward in time. The section highlighted in blue
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shows the period of time that is either skipped or repeated (during manual
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changes), or continuous (during time adjustments).</p>
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<br /><img src="rzati506.gif" alt="A manual change versus a time adjustment." /><br /><p>The <span class="uicontrol">Manual Change</span> shows that if you set the system
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time from 9:00 a.m. to 11:00 a.m. that the two-hour interval from 9:00 a.m.
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to 11:00 a.m. is skipped. Also, if you set the time backward from 11:00 a.m.
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to 9:00 a.m., the system time repeats the time frame from 9:00 a.m. to 11:00
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a.m.</p>
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<p>The <span class="uicontrol">Time Adjustment</span> shows that if you adjust the
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system time using the time adjustment function, the flow of time is neither
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skipped nor repeated. Time gradually speeds up or slows down until the desired
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time value is reached. The amount of time that an adjustment takes to complete
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depends on the length of the adjustment. A two-hour time adjustment, either
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negative or positive, is the maximum adjustment allowed. Time adjustments
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ensure that the system time flows continuously; therefore, time adjustments
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are the recommended method for changing system time.</p>
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<p>For more information about how to change the system time, either a manual
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time change or a time adjustment, see Update system time.</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="rzaticoncepts.htm" title="Use this information to understand time management concepts such as time zones, coordinated universal time (UTC), and daylight saving time (DST).">Concepts</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="rzatitimemainapp.htm" title="Use this information to learn how a typical time maintenance application works. You can also view an example environment that uses Simple Network Time Protocol (SNTP) as a time maintenance application.">Time maintenance application</a></div>
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<div><a href="rzati3minuteadj.htm" title="View this topic to learn how to manually adjust the system time by 3 minutes. A time adjustment is different from changing the time of day system value. A time adjustment is the recommended method for system time changes.">Scenario: Adjust the system time 3 minutes</a></div>
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</div>
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<div class="reltasks"><strong>Related tasks</strong><br />
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<div><a href="rzatiadjustsystime.htm" title="This topic provides details of how to update system time. You can adjust system time using a time adjustment, which is the preferred method, or manually change the system time using the time of day system value, if you need to change the system time immediately.">Update system time</a></div>
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<div><a href="rzatitimeoff.htm">System time is off more than 2 hours</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="../rzakz/rzakzqtime.htm">Time of day (QDATETIME) system value</a></div>
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</div>
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</div>
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</body>
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</html>
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