123 lines
7.4 KiB
HTML
123 lines
7.4 KiB
HTML
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<meta name="DC.Title" content="General operations for a distributed relational database" />
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<meta name="abstract" content="To plan for the general operation of a distributed relational database, consider both performance and availability." />
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<title>General operations for a distributed relational database</title>
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<body id="rbal1genop"><a name="rbal1genop"><!-- --></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">General operations for a distributed relational database</h1>
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<div><p>To plan for the general operation of a distributed relational database,
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consider both performance and availability.</p>
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<div class="section"><p>The following design considerations can help you improve both
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the performance and availability of a distributed relational database:</p>
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</div>
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<div class="section"><ul><li>If an application involves transactions that run frequently or that send
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or receive a lot of data, you should try to keep it in the same location as
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the data.</li>
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<li>For data that needs to be shared by applications in different locations,
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put the data in the location with the most activity.</li>
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<li>If the applications in one location need the data as much as the applications
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in another location, consider keeping copies of the data at both locations.
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When keeping copies at multiple locations, ask yourself the following questions
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about your management strategy: <ul><li>Will users be allowed to make updates to the copies?</li>
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<li>How and when will the copies be refreshed with current data?</li>
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<li>Will all copies have to be backed up or will backing up one copy be sufficient?</li>
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<li>How will general administration activities be performed consistently for
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all copies?</li>
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<li>When is it permissible to delete one of the copies?</li>
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</ul>
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</li>
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<li>Consider whether the distributed databases will be administered from a
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central location or from each database location.</li>
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</ul>
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</div>
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<div class="section"><p>You can also improve performance by doing the following things:</p>
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<ul><li>If data and applications must be kept at different locations, do the following
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things to keep the performance within acceptable limits: <ul><li>Keep data traffic across the network as low as possible by only retrieving
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the data columns that will be used by the application; that is, avoid using
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* in place of a list of column names as part of a SELECT statement.</li>
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<li>Discourage programmers from coding statements that send large amounts
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of data to or receive large amounts of data from a remote location; that is,
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encourage the use of the WHERE clause of the SELECT statement to limit the
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number of rows of data.</li>
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<li>Use referential integrity, triggers, and stored procedures (an SQL CALL
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statement after a CONNECT to a remote relational database management system);
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this improves performance by distributing processing to the application server
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(AS), which can substantially reduce line traffic.</li>
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<li>Use read-only queries where appropriate by specifying the FOR FETCH ONLY
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clause.</li>
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<li>Be aware of rules for blocking of queries. For example, in <span class="keyword">iSeries™</span>-to-<span class="keyword">iSeries</span> queries, blocking of read-only
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data is done only for COMMIT(*NONE), or for COMMIT(*CHG) and COMMIT(*CS) when
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ALWBLK(*ALLREAD) is specified.</li>
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<li>Keep the number of accesses to remote data low by using local data in
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place of remote data whenever possible.</li>
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<li>Use SQL set operations to process multiple rows at the application requester
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with a single SQL request.</li>
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<li>Try to avoid dropping of connections by using DDMCNV(*KEEP) when running
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with remote unit of work (RUW) connection management, or by running with distributed
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unit of work (DUW) connection management.</li>
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</ul>
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</li>
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<li>Provide sufficient network capacity by doing the following things:<ul><li>Increase the capacity of the network by installing high-speed, high-bandwidth
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lines or by adding lines at appropriate points in the network.</li>
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<li>Reduce the contention or improve the contention balance on certain processors.
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For example, move existing applications from a host server to a departmental
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server or group some distributed relational database work into batch.</li>
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</ul>
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</li>
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<li>Encourage good table design. At the distributed relational database locations,
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encourage appropriate use of primary keys, table indexes, and normalization
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techniques.</li>
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<li>Ensure data types of host variables used in WHERE clauses are consistent
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with the data types of the associated key column data types. For example,
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a floating-point host variable has been known to disqualify the use of an
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index built over a column of a different data type.</li>
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</ul>
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</div>
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<div class="section"><p>You can also improve availability by doing the following
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things:</p>
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<ul><li>In general, try to limit the amount of data traffic across the network.</li>
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<li>If data and applications must be kept at different locations, do the following
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things to keep the availability within acceptable limits: <ul><li>Establish alternate network routes.</li>
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<li>Consider the effect of time zone differences on availability: <ul><li>Will qualified people be available to bring up the server?</li>
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<li>Will off-hours batch work interfere with processing?</li>
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</ul>
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</li>
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<li>Ensure good backup and recovery features.</li>
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<li>Ensure people are skilled in backup and recovery.</li>
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</ul>
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</li>
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</ul>
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</div>
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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="rbal1managestrat.htm" title="When you are managing a distributed relational database, keep these strategies in mind.">Develop a management strategy for a distributed relational database</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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