97 lines
7.2 KiB
HTML
97 lines
7.2 KiB
HTML
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Time maintenance application" />
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<meta name="abstract" content="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." />
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<title>Time maintenance application</title>
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</head>
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<body id="rzatitimemainapp"><a name="rzatitimemainapp"><!-- --></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 maintenance application</h1>
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<div><p>Use this information to learn how a typical time maintenance application
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works. You can also view an example environment that uses Simple Network Time
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Protocol (SNTP) as a time maintenance application.</p>
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<p>A time maintenance application maintains the system time with an external
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time source. Each time maintenance application is unique and is programmed
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differently. However, the overall purpose of a time maintenance application
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is to retrieve a time value from an external time source and compare it to
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the system's time value. If the two values differ, a time adjustment begins.
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The amount of time that the two values must differ before a time adjustment
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begins is unique to the actual time maintenance application that you are using.</p>
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<p>Use the time adjustment (QTIMADJ) system value to identify the software
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to use to adjust the system clock to keep it synchronized with an external
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time source. The system does not enforce the software specified; it only identifies
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the software to use. This value should be maintained by the time adjustment
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software and is intended as an aid to prevent having multiple time adjustment
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applications conflict with each other. The system does not verify this value
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or that this software is or is not performing time adjustments. IBM<sup>®</sup> time adjustment
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offerings use identifiers that start with QIBM such as QIBM_OS400_SNTP. Other
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software suppliers should follow a similar naming convention of company name
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and product name.</p>
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<p>Time adjustment software should check this system value before starting.
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If this system value has an identifier for other time adjustment software,
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then the software being started should notify the user of this potential conflict
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and confirm that this time adjustment software should be started. When there
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is no identifier associated with this system value, the software should update
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this system value to identify that it is now responsible for adjusting the
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system clock. Time adjustment software should check this system value again
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before ending. This system value should be set to 'None' only if the current
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value identifies this time adjustment software that is ending.</p>
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<p>You can use the SNTP application to maintain your system time. The SNTP
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application is an IBM-supplied time maintenance application that you can use
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as a client, server, or both.</p>
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<div class="fignone" id="rzatitimemainapp__client"><a name="rzatitimemainapp__client"><!-- --></a><span class="figcap">Figure 1. SNTP as a client and a server</span><br /><img src="rzati501.gif" alt="Server A is the SNTP server and client" /><br /></div>
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<p>In <a href="#rzatitimemainapp__client">Figure 1</a>, the iSeries™ server
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(Server A) uses the SNTP application as a client and a server. The SNTP client
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retrieves a time value from an external time source. The external time source
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is determined by what you specify to use. The SNTP application synchronizes
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Server A's coordinated universal time (UTC) with the time value from the external
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time source. Then, the SNTP server (Server A) sends the time value to all
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SNTP client systems (iSeries Server B and Client A) connected to it.</p>
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<div class="fignone" id="rzatitimemainapp__sntp"><a name="rzatitimemainapp__sntp"><!-- --></a><span class="figcap">Figure 2. SNTP as a server</span><img src="rzati502.gif" alt="Server A is the SNTP server" /></div>
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<p>In <a href="#rzatitimemainapp__sntp">Figure 2</a>, the iSeries Server
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A uses the SNTP server. In this situation, the UTC time is retrieved from
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the iSeries server
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rather than being synchronized with an external time source. This internal
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time value is sent to all SNTP client systems (iSeries Server B and Client A) connected
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to it.</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="rzatitimeadj.htm" title="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.">Time adjustment</a></div>
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<div><a href="rzatisetuptimemain.htm" title="Find out how to use a time maintenance application to make the necessary adjustments to your system time.">Set up time maintenance</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/rzakzqtimadj.htm">Time adjustment (QTIMADJ) system value</a></div>
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<div><a href="../rzakt/rzaktkickoff.htm">Simple Network Time Protocol</a></div>
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</div>
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</div>
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</body>
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</html> |