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<title>Data Language Interface</title>

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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Data Language Interface</span></span>

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<div id="mw-content-text" class="mw-body-content mw-content-ltr" lang="en" dir="ltr"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><p><b>Data Language One</b> (Data Language/I, DL/I, Data Language/One, Data Language/One<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>) is the language system used to access <a href="IBM" title="IBM">IBM</a>'s <a href="IBM_Information_Management_System" title="IBM Information Management System">IMS</a> <a href="Database" title="Database">databases</a> and its <a href="Data_communication" title="Data communication">data communication</a> system.

</p><p>It is implemented from many languages by making calls to a software stub, DFSLI000. This stub has entry points to handle a variety of programming languages, e.g., calling CBLTDLI from a <a href="COBOL" title="COBOL">COBOL</a> program. This stub is linked to the calling program, passes on the request to the IMS system, and returns the results and a status code.

</p><p>In any full-function IMS database, the smallest element that can be retrieved is a <i>segment</i>. Each segment is made up of <i>fields</i>, one of which, typically, will be a key field. The segments are arranged hierarchically in the database, the highest-level segment type being a root segment. 255 different segment types, on up to 15 levels, are allowed in any database. A database <i>record</i> consists of a specific root segment and all its dependent child segments – there is no limit to the number of segments in a record, or to the number of records in a database (apart from the physical limitations of storage space).

</p><p>The structure of any database is presented to the application program as a <i>PCB</i> (Program Communication Block), and this is used as one of the <a href="Parameter_(computer_programming)" title="Parameter (computer programming)">parameters</a> passed to the stub. Other types of PCB are used to send and receive <a href="Transaction_processing" title="Transaction processing">transaction processing</a> messages, access and write to the user’s <a href="Computer_monitor" title="Computer monitor">VDU</a> screen, and to print reports, etc.

</p><p>When accessing a database segment, the application program also uses an <i>SSA</i> (Segment Search Argument) as a parameter, to specify the segment or segments that it needs. This would typically contain the segment type required and the contents of any key fields.

</p><p>For all languages except <a href="PL/I" title="PL/I">PL/I</a>, the first parameter in a call is the <i>Function Code</i> – a four-character field, examples being: “<code>GU  </code>” (Get Unique), “<code>GN  </code>” (Get Next), “<code>REPL</code>” (Replace), and “<code>ISRT</code>” (Insert). With PL/I, due to the way this language does not mark the last parameter with a '1' in bit 0, the first parameter must instead be a fullword (Fixed Bin(31)) containing the number of following parameters.

</p><p>A typical call from a <a href="COBOL" title="COBOL">COBOL</a> program might be <code class="mw-highlight mw-highlight-lang-cobolfree mw-content-ltr" dir="ltr"><span class="kr">CALL </span><span class="err">“</span><span class="nv">CBLTDLI</span><span class="err">”</span><span class="w"> </span><span class="kp">USING</span><span class="w"> </span><span class="nv">GU</span><span class="p">,</span><span class="w"> </span><span class="nv">Stores-Database-PCB</span><span class="p">,</span><span class="w"> </span><span class="nv">Stores-Segment-Area</span><span class="p">,</span><span class="w"> </span><span class="nv">Stores-Root-SSA</span></code>. The program would then automatically wait till the requested data were retrieved and placed in the Segment-Area. The status code contained within the PCB would be updated with either blanks (if all went well) or some informational or error code.

</p><p>A typical call from a PL/I program might be <code class="mw-highlight mw-highlight-lang-cobolfree mw-content-ltr" dir="ltr"><span class="kr">CALL</span><span class="w"> </span><span class="nv">PLITDLI</span><span class="p">(</span><span class="nv">FOUR</span><span class="p">,</span><span class="w"> </span><span class="nv">GU</span><span class="p">,</span><span class="w"> </span><span class="nv">Stores-Database-PCB</span><span class="p">,</span><span class="w"> </span><span class="nv">Stores-Segment-Area</span><span class="p">,</span><span class="w"> </span><span class="nv">Stores-Root-SSA</span><span class="p">);</span></code>.

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<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20060321113510/http://www-03.ibm.com/servers/eserver/zseries/zvse/products/database.html#dli">"IBM z/VSE Products and components"</a>. <a href="IBM" title="IBM">IBM</a>. Archived from <a rel="nofollow" class="external text" href="http://www-03.ibm.com/servers/eserver/zseries/zvse/products/database.html#dli">the original</a> on March 21, 2006<span class="reference-accessdate">. Retrieved <span class="nowrap">2009-06-27</span></span>.</cite></span>

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<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><a rel="nofollow" class="external text" href="http://publib.boulder.ibm.com/infocenter/dzichelp/v2r2/index.jsp">Information Management Software for z/OS Solutions Information Center</a></li>

<li><a rel="nofollow" class="external text" href="http://publib.boulder.ibm.com/infocenter/iadthelp/v6r0/index.jsp?topic=/com.ibm.etools.egl.doc/topics/ceglasm0401.html">Basic DL/I database concepts</a></li></ul></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2025-03-09" href="https://en.wikipedia.org/wiki/?title=Data_Language_Interface&oldid=1279684053">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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