216 lines
11 KiB
HTML
216 lines
11 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="DC.Title" content="ISO/ANSI standard data set label 2 (HDR2/EOV2/EOF2)" />
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<meta name="abstract" content="The ISO/ANSI standard data set label 2 (HDR2/EOV2/TRL2) is 80 characters in length and is used to identify additional information about the data set. The system records the data set label in ASCII." />
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<meta name="description" content="The ISO/ANSI standard data set label 2 (HDR2/EOV2/TRL2) is 80 characters in length and is used to identify additional information about the data set. The system records the data set label in ASCII." />
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<meta name="DC.Relation" scheme="URI" content="volum.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2004, 2006" />
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<title>ISO/ANSI standard data set label 2 (HDR2/EOV2/EOF2)</title>
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</head>
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<body id="ahdr2d"><a name="ahdr2d"><!-- --></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">ISO/ANSI standard data set label 2 (HDR2/EOV2/EOF2)</h1>
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<div><p>The ISO/ANSI standard data set label 2 (HDR2/EOV2/TRL2) is 80 characters
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in length and is used to identify additional information about the data set.
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The system records the data set label in ASCII.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" width="100%" frame="hsides" border="0" rules="none"><caption>Table 1. Format of the IBM<sup>®</sup> Standard Data
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Set Label 2 (HDR2/EOV2/EOF2)</caption><thead align="left"><tr><th align="left" valign="bottom" width="9.945750452079565%" id="d0e25">Offset</th>
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<th align="left" valign="bottom" width="14.466546112115733%" id="d0e27">Data type</th>
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<th align="left" valign="bottom" width="10.849909584086799%" id="d0e29">Length</th>
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<th align="left" valign="bottom" width="64.73779385171791%" id="d0e31">Contents</th>
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</tr>
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</thead>
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<tbody><tr><td align="left" valign="top" width="9.945750452079565%" headers="d0e25 ">0</td>
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<td align="left" valign="top" width="14.466546112115733%" headers="d0e27 ">Character</td>
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<td align="left" valign="top" width="10.849909584086799%" headers="d0e29 ">3</td>
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<td align="left" valign="top" width="64.73779385171791%" headers="d0e31 ">Label identifier</td>
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</tr>
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<tr><td align="left" valign="top" width="9.945750452079565%" headers="d0e25 ">3</td>
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<td align="left" valign="top" width="14.466546112115733%" headers="d0e27 ">Character</td>
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<td align="left" valign="top" width="10.849909584086799%" headers="d0e29 ">1</td>
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<td align="left" valign="top" width="64.73779385171791%" headers="d0e31 ">Label number</td>
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</tr>
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<tr><td align="left" valign="top" width="9.945750452079565%" headers="d0e25 ">4</td>
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<td align="left" valign="top" width="14.466546112115733%" headers="d0e27 ">Character</td>
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<td align="left" valign="top" width="10.849909584086799%" headers="d0e29 ">1</td>
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<td align="left" valign="top" width="64.73779385171791%" headers="d0e31 ">Record Format</td>
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</tr>
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<tr><td align="left" valign="top" width="9.945750452079565%" headers="d0e25 ">5</td>
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<td align="left" valign="top" width="14.466546112115733%" headers="d0e27 ">Character</td>
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<td align="left" valign="top" width="10.849909584086799%" headers="d0e29 ">5</td>
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<td align="left" valign="top" width="64.73779385171791%" headers="d0e31 ">Block Length</td>
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</tr>
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<tr><td align="left" valign="top" width="9.945750452079565%" headers="d0e25 ">10</td>
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<td align="left" valign="top" width="14.466546112115733%" headers="d0e27 ">Character</td>
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<td align="left" valign="top" width="10.849909584086799%" headers="d0e29 ">5</td>
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<td align="left" valign="top" width="64.73779385171791%" headers="d0e31 ">Record Length</td>
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</tr>
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<tr><td align="left" valign="top" width="9.945750452079565%" headers="d0e25 ">15</td>
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<td align="left" valign="top" width="14.466546112115733%" headers="d0e27 ">Character</td>
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<td align="left" valign="top" width="10.849909584086799%" headers="d0e29 ">35</td>
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<td align="left" valign="top" width="64.73779385171791%" headers="d0e31 ">Reserved for Operating System</td>
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</tr>
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<tr><td align="left" valign="top" width="9.945750452079565%" headers="d0e25 ">50</td>
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<td align="left" valign="top" width="14.466546112115733%" headers="d0e27 ">Character</td>
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<td align="left" valign="top" width="10.849909584086799%" headers="d0e29 ">2</td>
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<td align="left" valign="top" width="64.73779385171791%" headers="d0e31 ">Buffer offset</td>
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</tr>
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<tr><td align="left" valign="top" width="9.945750452079565%" headers="d0e25 ">52</td>
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<td align="left" valign="top" width="14.466546112115733%" headers="d0e27 ">Character</td>
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<td align="left" valign="top" width="10.849909584086799%" headers="d0e29 ">28</td>
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<td align="left" valign="top" width="64.73779385171791%" headers="d0e31 ">Reserved</td>
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</tr>
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</tbody>
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</table>
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</div>
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<p>The manual describes the contents and function of each of the following
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fields.</p>
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<ul><li>Label identifier <div class="p">The characters identify the type of data set label.
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<dl><dt class="dlterm">HDR</dt>
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<dd>Header Label (the beginning of a data set)</dd>
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<dt class="dlterm">EOF</dt>
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<dd>Trailer Label (the end of a data set)</dd>
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<dt class="dlterm">EOV</dt>
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<dd>Trailer Label (the end of a data set that is continued on another volume)</dd>
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</dl>
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</div>
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</li>
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<li>Label number <p>The relative position of this label within the set of
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labels of the same type; it is always 2 for the data set label 2.</p>
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</li>
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<li>Record Format <div class="p">An alphabetic character that indicates the format of
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the records in the data set. The record format indicates to the operating
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system how to interpret the blocks of data that the program reads from the
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tape volume. <dl><dt class="dlterm">F</dt>
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<dd>Fixed length records</dd>
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<dt class="dlterm">V</dt>
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<dd>Variable length records</dd>
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<dt class="dlterm">U</dt>
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<dd>Undefined length records</dd>
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</dl>
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</div>
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</li>
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<li>Block Length <p>A number indicating the block length, in bytes, of the
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data blocks on the tape. The number in this field can range from 18 to 2048.
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This block length should include the buffer offset and padding.</p>
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<p>Note
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that the 18-byte to 2048 byte limit on block length is an ISCII/ASCII standard.
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You can specify larger blocks (up to 9999 bytes) with the agreement of the
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interchange parties. However, for tapes with Version 3 labels, exceeding the
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2048 byte limit might create incompatible tapes.</p>
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<div class="p">Interpretation of
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the number depends on the associated record format field as follows: <dl><dt class="dlterm">Record format F</dt>
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<dd>Maximum block length.</dd>
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<dt class="dlterm">Record format D</dt>
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<dd>Maximum block length that includes the 4 byte length indicator in the
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records and the optional block prefix.</dd>
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<dt class="dlterm">Record format S</dt>
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<dd>Maximum block length that includes the optional block prefix, plus one
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or more pairs of 5 byte segment control words and segments.</dd>
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</dl>
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</div>
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</li>
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<li>Record Length <div class="p">A number indicating the record length, in bytes, of
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the logical records on the tape volume. The interpretation of the number depends
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on the Record Format field. <ul><li>Record format F <p>Actual record length</p>
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</li>
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<li>Record format D <p>Maximum record length that includes the 4 byte length
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indicator in the records</p>
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</li>
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<li>Record format S <p>Maximum record length that excludes all the 5 byte
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segment control words that describe the record. If the record length is larger
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than 99999, this field is 0.</p>
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</li>
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</ul>
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</div>
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</li>
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<li>Reserved for Operating System <div class="p">The content of this field is optional
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for each operating system. <span class="keyword">i5/OS™</span> has
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chosen similar meaning to the same bytes in the IBM Standard Data Set Label 2. <ul><li>Tape Density (1 byte) <dl><dt class="dlterm">3</dt>
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<dd>1600 bpi</dd>
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<dt class="dlterm">4</dt>
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<dd>3200 bpi</dd>
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<dt class="dlterm">5</dt>
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<dd>6250 bpi</dd>
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<dt class="dlterm">blank</dt>
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<dd>All other densities/formats</dd>
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</dl>
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</li>
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<li>Data Set Position (1 byte) <div class="p">A code indicating a volume switch is as
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follows: <dl><dt class="dlterm">0</dt>
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<dd>No volume switch has occurred</dd>
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<dt class="dlterm">1</dt>
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<dd>A volume switch previously occurred</dd>
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</dl>
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</div>
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</li>
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<li>Job/Job Step Identification (17 bytes) <p>This field identifies the job
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and job step that created or extended the data set. <span class="keyword">i5/OS</span> does not use this field.</p>
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</li>
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<li>Tape Recording Technique (2 bytes) <div class="p">This field indicates the tape recording
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technique used in creating the data set. <dl><dt class="dlterm">blank</dt>
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<dd>No Improved Data Recording Capability (IDRC) used.</dd>
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<dt class="dlterm">'P '</dt>
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<dd>Improved Data Recording Capability (IDRC) used.</dd>
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</dl>
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</div>
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</li>
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<li>Control Character (1 byte) <div class="p">A printer control code indicating whether
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the program uses a control character set to create the data set and the type
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of control characters the program uses: <dl><dt class="dlterm">A</dt>
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<dd>Contains ISO/ANSI control letters</dd>
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<dt class="dlterm">blank</dt>
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<dd>Contains no control characters</dd>
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</dl>
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</div>
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</li>
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<li>Buffer Alignment Block (1 byte) <p><span class="keyword">i5/OS</span> does not use this field.</p>
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</li>
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<li>Block Attribute <div class="p">A code indicating the block attribute used to create
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the data set: <dl><dt class="dlterm">B</dt>
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<dd>Blocked records</dd>
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<dt class="dlterm">blank</dt>
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<dd>Records not blocked</dd>
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</dl>
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</div>
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</li>
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<li>Reserved (11 bytes) <p><span class="keyword">i5/OS</span> does not use this field.</p>
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</li>
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</ul>
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</div>
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</li>
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<li>Buffer Offset <p>The length of the block prefix (from 0 to 99). Used
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to determine the length of an optional prefix that might be a part of a physical
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block on tape. The version of the prefix for variable and spanned record formats
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is known as a block descriptor word (BDW). A BDW is always 4 bytes long and
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contains the block length of the physical record it describes, including the
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BDW.</p>
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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 class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="volum.htm" title="This topic describes the volume labels used in the open feedback area.">Volume label fields</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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