108 lines
7.6 KiB
HTML
108 lines
7.6 KiB
HTML
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<meta name="DC.Title" content="LOB file reference variables" />
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<meta name="abstract" content="File reference variables are similar to host variables except that they are used to transfer data to and from IFS files (not to and from memory buffers)." />
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<meta name="description" content="File reference variables are similar to host variables except that they are used to transfer data to and from IFS files (not to and from memory buffers)." />
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<meta name="DC.subject" content="LOBs (Large Objects), file reference variables, input values, file reference variables, SQL_FILE_READ, input value option, LOBs (Large Objects), output values, SQL_FILE_CREATE, output value option, SQL_FILE_OVERWRITE, output value option, SQL_FILE_APPEND, output value option" />
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<title>LOB file reference variables</title>
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<body id="rbafylobrefvar"><a name="rbafylobrefvar"><!-- --></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">LOB file reference variables</h1>
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<div><p>File reference variables are similar to host variables except that
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they are used to transfer data to and from IFS files (not to and from memory
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buffers).</p>
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<div class="section"><p>A file reference variable represents (rather than contains) the
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file, just as a LOB locator represents (rather than contains) the LOB value.
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Database queries, updates, and inserts may use file reference variables to
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store, or to retrieve, single LOB values.</p>
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</div>
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<div class="section"><p>For very large objects, files are natural containers. It is likely
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that most LOBs begin as data stored in files on the client before they are
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moved to the database on the server. The use of file reference variables assists
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in moving LOB data. Programs use file reference variables to transfer LOB
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data from the IFS file directly to the database engine. To carry out the
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movement of LOB data, the application does not need to write utility routines
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to read and write files using host variables.</p>
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</div>
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<div class="section"> <div class="note"><span class="notetitle">Note:</span> The file referenced by the file reference variable must be
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accessible from (but not necessarily resident on) the system on which the
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program runs. For a stored procedure, this is the server.</div>
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</div>
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<div class="section"><p>A file reference variable has a data type of BLOB, CLOB, or DBCLOB.
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It is used either as the source of data (input) or as the target of data
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(output). The file reference variable may have a relative file name or a
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complete path name of the file (the latter is advised). The file name length
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is specified within the application program. The data length portion of the
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file reference variable is unused during input. During output, the data length
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is set by the application requester code to the length of the new data that
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is written to the file.</p>
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</div>
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<div class="section"><p>When using file reference variables there are different options
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on both input and output. You must choose an action for the file by setting
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the <samp class="codeph">file_options</samp> field in the file reference variable structure.
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Choices for assignment to the field covering both input and output values
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are shown below.</p>
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</div>
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<div class="section"><p>Values (shown for C) and options when using input file reference
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variables are as follows:</p>
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<ul><li><strong>SQL_FILE_READ</strong> (Regular file) — This option has a value of 2. This
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is a file that can be open, read, and closed. DB2<sup>®</sup> determines the length of the data in
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the file (in bytes) when opening the file. DB2 then returns the length through the <samp class="codeph">data_length</samp>
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field of the file reference variable structure. The value for COBOL is SQL-FILE-READ.</li>
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</ul>
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</div>
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<div class="section"><p>Values and options when using output file reference variables
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are as follows:</p>
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<ul><li><strong>SQL_FILE_CREATE</strong> (New file) — This option has a value of 8. This
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option creates a new file. Should the file already exist, an error message
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is returned. The value for COBOL is SQL-FILE-CREATE. </li>
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<li><strong>SQL_FILE_OVERWRITE</strong> (Overwrite file) — This option has a value
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of 16. This option creates a new file if none already exists. If the file
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already exists, the new data overwrites the data in the file. The value for
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COBOL is SQL-FILE-OVERWRITE.</li>
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<li><strong>SQL_FILE_APPEND</strong> (Append file) — This option has a value of 32.
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This option has the output appended to the file, if it exists. Otherwise,
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it creates a new file. The value for COBOL is SQL-FILE-APPEND.</li>
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</ul>
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<div class="note"><span class="notetitle">Note:</span> If a LOB file reference variable is used in an OPEN statement,
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do not delete the file associated with the LOB file reference variable until
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the cursor is closed.</div>
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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="rbafylobs.htm" title="The VARCHAR, VARGRAPHIC, and VARBINARY data types have a limit of 32 KB (where KB equals 1024 bytes) of storage. While this may be sufficient for small to medium-size text data, applications often need to store large text documents. They might also need to store a wide variety of additional data types such as audio, video, drawings, mixed text and graphics, and images. There are three data types to store these data objects as strings of up to 2 GB (where GB equals 1 073 741 824 bytes).">Use large objects (LOBs)</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="rbafyloblocators.htm" title="Large object (LOB) locators use a small, easily managed value to refer to a much larger value.">Understand large object locators</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="../ifs/rzaaxkickoff.htm">Integrated file system</a></div>
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</div>
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</div>
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</body>
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