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117 lines
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<meta name="DC.Title" content="Batch file processing with DDM" />
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<meta name="abstract" content="Consider these items when using batch file processing with DDM." />
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<title>Batch file processing with DDM</title>
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<body id="rbae5batchproc"><a name="rbae5batchproc"><!-- --></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">Batch file processing with DDM</h1>
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<div><p>Consider these items when using batch file processing with DDM.</p>
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<div class="section"><ul><li>When an application opens a local file for <em>sequential input only</em> or <em>output
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add</em>, the server uses blocking techniques to achieve maximum throughput.
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To ensure blocking is used for a remote file accessed by using DDM, do not
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use random record processing operations in the program but specify OVRDBF
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SEQONLY(*YES) against the DDM files opened by the program.</li>
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<li>Use of read and read-next operations in the high-level language (HLL)
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program to access the file maximizes the effect of the SEQONLY(*YES) specification.</li>
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<li>The use of random processing operations, such as chain operations of ILE
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RPG or start operations of ILE COBOL programming language, causes DDM to send
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deblocked operations across the communications line even if the application
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processes the file data sequentially. This results in significant differences
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between local and remote file processing.</li>
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<li>When simple physical file transfer is desired (all records transferred
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and no application processing of the data), use of DDM by using the <span class="cmdname">Copy
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File (CPYF)</span> command, or a user-written program using DDM with the <span class="cmdname">Override
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Database File (OVRDBF)</span> command SEQONLY(*YES number-of-records) specified,
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transfers the data more quickly than a user-written APPC program. The <span class="cmdname">Copy
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File</span> command and the DDM SEQONLY(*YES) support require less calls
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and returns between the program and APPC data management modules than does
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a standard ILE RPG or ILE COBOL APPC program.</li>
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<li>For ILE RPG or ILE COBOL sequential input-only applications, SEQONLY(*YES)
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should be specified with no <em>number of records</em> to achieve best throughput.
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For ILE RPG or ILE COBOL sequential output-only applications to keyed files,
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a large <em>number-of-records</em> value should be used.</li>
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<li>The <span class="cmdname">Send Network File (SNDNETF)</span> command can be considered
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as an alternative to DDM or user-written APPC programs when transferring all
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records within a file to a remote <span class="keyword">iSeries™ server</span>.
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The <span class="cmdname">SNDNETF</span> command requires SNADS to be configured on
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the source and target <span class="keyword">iSeries server</span>.
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If one or more intermediate servers are between the source and target <span class="keyword">iSeries server</span>s, SNADS provides intermediate
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node routing of the data when correctly configured.</li>
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<li>Use of the <span class="cmdname">SNDNETF</span> command by using SNADS offers the
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advantages of transmitting one copy of the data to multiple users on one or
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more target servers through a multiple node network, and the time scheduled
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transmission of that data by using the SNADS distribution queue parameter.
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<p>However, in addition to requiring SNADS to use the <span class="cmdname">SNDNETF</span> command,
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the target server user must also run the <span class="cmdname">Receive Network File (RCVNETF)</span> command
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to make the file usable on the target server. Use of DDM would not require
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this additional target server processing. </p>
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<p>In general, the file transmission times by using SNADS (user program DDM
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sequential file processing, the DDM <span class="cmdname">Copy File</span> command,
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and a user-written APPC program between two <span class="keyword">iSeries server</span>s)
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are within 10% of each other. However, the use of the <span class="cmdname">SNDNETF</span> and <span class="cmdname">RCVNETF</span> commands
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to make a copy of the data usable on the target server does add total processing
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time over the other methods of file transfer.</p>
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</li>
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<li>Because the <span class="cmdname">SNDNETF</span> command can transmit objects within
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a save file, the amount of data that is actually sent by using this technique
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might be less than that sent using the other techniques. If the database file
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data sent contains a significant number of duplicate character strings, use
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of the <span class="cmdname">Save Object (SAVOBJ)</span> command parameter DTACPR(*YES)
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(data compression) can significantly reduce the amount of data that is actually
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sent by using a SNADS distribution. However, if there are few
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duplicate character strings, there is little change in the amount of data
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sent.</li>
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<li>The <span class="keyword">iSeries</span> file transfer
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subroutines might also be used to transfer an entire file between <span class="keyword">iSeries server</span>s and an <span class="keyword">iSeries server</span> and
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a <span class="keyword">System/36™</span>. These subroutines
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might be called from high-level language programs, and in some cases throughput
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is achieved similar to that by using DDM.</li>
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</ul>
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<p>See the <em>SNA Distribution Services</em> manual on the <a href="http://publib.boulder.ibm.com/iseries/v5r1/ic2924/rzaqhindex.htm">V5R1
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Supplemental Manuals</a><img src="www.gif" alt="Link outside information center" /> Web site.</p>
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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="rbae5perfcon.htm" title="These topics provide information to help you improve performance when using DDM and also provide some information about when to use something other than DDM to accomplish some functions.">Performance considerations for DDM</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="../books/sc415406.pdf" target="_blank">Communications Management PDF</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="rbae5objdist.htm" title="Although DDM file names can be specified on the Send Network File (SNDNETF) and Receive Network File (RCVNETF) commands, these commands should be run, whenever possible, on the server where the data actually exists. Therefore, if both servers are iSeries servers and both are part of a SNADS network, object distribution can be used instead of DDM to transfer the data between them.">Use of object distribution</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../books/sc415442.pdf " target="_blank">ICF Programming PDF</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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