90 lines
6.9 KiB
HTML
90 lines
6.9 KiB
HTML
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<meta name="DC.Title" content="Reasons to journal access paths" />
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<title>Reasons to journal access paths</title>
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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">Reasons to journal access paths</h1>
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<div><p>If you journal access paths, the system can use the journal entries
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to recover access paths instead of rebuilding them completely.</p>
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<p>When your server ends abnormally, perhaps because of a power interruption,
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the next IPL can take much longer than a normal IPL. Rebuilding access paths
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contributes to this long IPL time. When you perform an IPL after an abnormal
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end, the system rebuilds access paths that were exposed, except those access
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paths that are specified as MAINT(*REBLD) when you create the file. An access
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path is exposed if changes have been made to it that have not been written
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to the disk.</p>
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<p>If you journal access paths, the system can use the journal entries to
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recover access paths instead of rebuilding them completely. This reduces the
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time it takes to IPL after the system ends abnormally. Access path journaling
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is strictly for the purpose of server recovery during an IPL. You do not use
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access path journal entries when you are applying journal changes to recover
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a file.</p>
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<p>If certain access paths and their underlying files are critical to your
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operation, you want to ensure that these files are available as soon as possible
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after the system ends abnormally. You can choose to journal these access paths.
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This is called <span class="uicontrol">explicit access path journaling</span>.</p>
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<p>Explicit access path journaling differs system-managed access-path protection
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(SMAPP) in that with SMAPP you cannot control which access paths the system
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chooses to protect. Therefore, if the system does not protect the access path
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that you consider critical to meet your target recovery times, you must explicitly
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journal that access path.</p>
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<p>If you choose to journal an access path, remember the following:</p>
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<ul><li>You can journal an access path for a physical file only if the physical
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file has a keyed access path or an index created by a referential constraint.</li>
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<li>Before you start journaling an access path, you must journal all the underlying
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physical files to the same journal.</li>
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<li>You can journal only access paths that are defined as MAINT(*IMMED) or
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MAINT(*DLY).</li>
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<li><img src="./delta.gif" alt="Start of change" />Some access paths with international components for unicode
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(ICU) sort sequence tables are too complex to be journaled. You
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can journal access paths with other sort sequence tables, and many of the
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access paths with ICU sort sequence tables.<img src="./deltaend.gif" alt="End of change" /></li>
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</ul>
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<p>The System-managed access-path protection topic has detailed information
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about SMAPP.</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> <img src="./delta.gif" alt="Start of change" /><a href="rzakiplnobjrn.htm" title="When you plan which objects to journal, consider the following:">Plan which objects to journal</a><img src="./deltaend.gif" alt="End of change" /></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="rzakismappapjourn.htm" title="In addition to using system-managed access path protection (SMAPP), you can choose to journal some access paths yourself by using the Start Journaling Access Path (STRJRNAP) command. This is called explicit journaling.">SMAPP and access path journaling</a></div>
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<div><a href="rzakismappintro.htm" title="System-managed access-path protection (SMAPP) allows you to use some of the advantages of journaling without explicitly setting up journaling. Use SMAPP to decrease the time it takes to restart your system after an abnormal end.">System-managed access-path protection</a></div>
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<div><a href="rzakijklprod.htm" title="JKLPROD is the system that JKL uses for all of their customer orders and where their business applications are installed (inventory control, customer orders, contracts and pricing, accounts receivable). The information about this server is extremely critical to their business and changes often.">JKLPROD</a></div>
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<div><a href="rzakijkldev.htm" title="JKLDEV is JKL's development server. Though it does not require 24x7 availability, the data on it represent many person hours of work by the developers. Therefore it is important that in the event of a crash, the system be brought to a current state. Also, since it is a development server, changes to the data occur often.">JKLDEV</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="rzakistrjrnap.htm" title="After you have started journaling for physical files, you can set up explicit journaling of access paths.">Journal access paths</a></div>
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