65 lines
5.0 KiB
HTML
65 lines
5.0 KiB
HTML
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<!DOCTYPE html
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Describe floating-point fields in logical files" />
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<meta name="abstract" content="You can use floating-point fields as mapped fields in logical files. A single- or double-precision floating-point field can be mapped to or from a zoned, packed, zero-precision binary, or another floating-point field. You cannot map between a floating-point field and a nonzero-precision binary field, a character field, a hexadecimal field, or a double-byte character set (DBCS) field." />
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<title>Describe floating-point fields in logical files</title>
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<body id="rbafofpdbc"><a name="rbafofpdbc"><!-- --></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">Describe floating-point fields in logical files</h1>
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<div><p>You can use floating-point fields as mapped fields in logical files.
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A single- or double-precision floating-point field can be mapped to or from
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a zoned, packed, zero-precision binary, or another floating-point field. You
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cannot map between a floating-point field and a nonzero-precision binary field,
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a character field, a hexadecimal field, or a double-byte character set (DBCS)
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field.</p>
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<p>Mapping between floating-point fields of different precision, single or
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double, or between floating-point fields and other numeric fields, can result
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in rounding or a loss of precision. Mapping a double-precision floating-point
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number to a single-precision floating-point number can result in rounding,
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depending on the particular number involved and its internal representation.
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Rounding is to the nearest (even) bit. The result always contains as much
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precision as possible. A loss of precision can also occur between
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two decimal numbers if the number of digits of precision is decreased.</p>
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<p>You can inadvertently change the value of a field which your program did
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not explicitly change. For floating-point fields, this can occur if a physical
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file has a double-precision field that is mapped to a single-precision field
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in a logical file, and you issue an update for the record through the logical
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file. If the internal representation of the floating-point number causes it
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to be rounded when it is mapped to the logical file, then updating the logical
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record causes a permanent loss of precision in the physical file. If the rounded
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number is the key of the physical record, then the sequence of records in
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the physical file can also change.</p>
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<p>A fixed-point numeric field can also be updated inadvertently if the precision
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is decreased in the logical file.</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="rbafodrflf.htm" title="For every logical file record format described with data description specifications (DDS), you must specify a record format name and either the PFILE keyword (for simple and multiple format logical files), or the JFILE keyword (for join logical files).">Describe logical file record formats</a></div>
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</div>
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</div>
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</body>
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