83 lines
5.7 KiB
HTML
83 lines
5.7 KiB
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<meta name="DC.Title" content="Data redundancy in your distributed relational database network" />
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<meta name="abstract" content="Data redundancy in a distributed relational database also provides different ways for users on the distributed relational database network to access a database on the network." />
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<title>Data redundancy in your distributed relational database network</title>
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<body id="rbal1dataredund"><a name="rbal1dataredund"><!-- --></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">Data redundancy in your distributed relational database network</h1>
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<div><p>Data redundancy in a distributed relational database also provides
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different ways for users on the distributed relational database network to
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access a database on the network.</p>
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<p>The considerations a distributed relational database administrator examines
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to create a data redundancy strategy are more complex than ensuring communications
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paths are available to the data.</p>
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<p>Tables can be replicated across servers in the network, or a snapshot of
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data can be used to provide data availability. <span>DataPropagator™ for iSeries™,
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V8.1</span> can provide this capability.</p>
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<p>The following figure shows that a copy of the MP000 server distributed
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relational database can be stored on the KC000 server, and a copy of the KC000
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server distributed relational database can be stored on the MP000 server.
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The application requester (AR) from one region can link to the other application
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server (AS) to query or to update a replicated copy of their relational database.</p>
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<div class="fignone"><span class="figcap">Figure 1. Data redundancy example</span><br /><img src="rbal1505.gif" alt="Data Redundancy Example" /><br /></div>
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<p>The administrator must decide what is the most efficient, effective strategy
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to allow distributed relational database processing. Alternative strategies
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might include these scenarios.</p>
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<p>One alternative might be that when MP000 is unavailable, its ARs connect
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to the KC000 server to query a read-only snapshot of the MP000 distributed
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relational database so service work can be scheduled.</p>
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<p><span>DataPropagator for iSeries, V8.1</span> can provide a read-only
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copy (or <em>snapshot</em>) of the tables to a remote server on a regular basis.
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For the Spiffy Corporation, this might be at the end or the beginning of each
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business day. In this example, the MP000 database snapshot provides a 24-hour-old,
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last-point-in-time picture for dealerships to use for scheduling only. When
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the MP000 server is back on line, its ARs query the MP000 distributed relational
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database to completely process inventory requests or other work queried on
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the snapshot.</p>
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<p>Another alternative might be that Spiffy Corporation wants dealership users
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to be able to update a replicated table at another AS when their regional
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AS is unavailable.</p>
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<p>For example, an AR that normally connects to the MP000 database could connect
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to a replicated MP000 database on the KC000 server to process work. When the
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MP000 server is available again, the MP000 relational database can be updated
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by applying journal entries from activity originating in its replicated tables
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at the KCOOO location. When these journal entries have been applied to the
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original MP000 tables, distributed relational database users can access the
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MP000 as an AS again.</p>
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<p>Journal management processes on each regional server update all relational
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databases. The amount of journal management copy activity in this situation
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should be examined because of potential adverse performance effects at these
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servers.</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="rbal1recover.htm" title="In a distributed relational database environment, data availability not only involves protecting data on an individual server in the network, but also ensuring that users have access to the data across the network.">Data availability and protection</a></div>
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</div>
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</div>
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</body>
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