88 lines
5.8 KiB
HTML
88 lines
5.8 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Programming interfaces (HPOFS)" />
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<meta name="abstract" content="You can create or read files on HPOFS media by using either the Hierarchical File System (HFS) application programming interface (API) or the integrated file system application programming interface (API)." />
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<title>Programming interfaces (HPOFS)</title>
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</head>
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<body id="rzam4hpofsproginter"><a name="rzam4hpofsproginter"><!-- --></a>
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<img src="./delta.gif" alt="Start of change" /><!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Programming interfaces (HPOFS)</h1>
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<div><p>You can create or read files on HPOFS media by using either the
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Hierarchical File System (HFS) application programming interface (API) or
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the integrated file system application programming interface (API).</p>
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<p> The following are items specific to the i5/OS™ implementation of the HPOFS media
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format that application developers need to know.</p>
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<dl><dt class="dlterm">National Language Support</dt>
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<dd>The integrated file system interfaces assume that the coded character
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set identifier (CCSID) represents the path in effect for the job. The system
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then converts the path from the job CCSID to an internally used CCSID. The
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HFS interface makes no assumption about the CCSID of the path; therefore,
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the system performs no character set conversion on the path. This could produce
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undesirable side effects if an application used the two API sets interchangeably
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or if the application changed from using one API set to the other.</dd>
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<dd class="ddexpand">A program should not create files through HFS and then try to read them
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by using the integrated file system APIs. Depending on the characters that
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are used in the path name, this could result in a <tt class="msgph">File not found</tt> error.
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This type of problem can be avoided if the application uses only invariant
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characters (for example A-Z 0-9 + = % & ( ) , _ . : ;) for path names.
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Invariant characters are graphic characters that map to the same code point
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in all character sets.</dd>
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</dl>
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<dl><dt class="dlterm">Held optical files</dt>
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<dd>When the system writes an optical file that it cannot close normally,
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the system may create a held optical file. The held file exists on i5/OS internal
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disk storage and contains the data written to the file. You can then save
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or release the held file through an API or command interface. The system creates
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held files only when files fail to archive on HPOFS media.</dd>
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</dl>
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<dl><dt class="dlterm">Synchronous writes</dt>
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<dd>You can open files on HPOFS through HFS by specifying that all write operations
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be synchronous. When specified, write operations will be synchronous to i5/OS internal
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disk storage, not to the optical media. In the event of a power failure the
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data is recoverable from a held optical file. </dd>
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<dd class="ddexpand">Similarly for the HFS <span class="apiname">Force Buffered Data</span> API and the <span class="apiname">integrated
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file system fsync()</span> API, data will be forced to i5/OS internal
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disk storage, not to optical. Again, in the event of a power failure, the
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data is recoverable from a held optical file.</dd>
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</dl>
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<dl><dt class="dlterm">File sharing</dt>
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<dd>Multiple jobs or threads can share files. The system fully recognizes
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files that share modes as specified on the open request. For example, assume
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that a job opens a file that specifies it to share only with readers. This
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means that you can perform other opens only as long as the access requested
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remains read only.</dd>
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</dl>
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<dl><dt class="dlterm">Extended file attributes</dt>
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<dd>The system supports extended file attributes for files on HPOFS media.
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Extended attributes can be written to files using the HFS Change Directory
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Entry Attributes API as well as through some integrated file system interfaces.</dd>
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</dl>
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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="rzam4highperfofs.htm" title="High performance optical file system (HPOFS) is an IBM-developed media format architecture available to use when initializing optical media on the i5/OS.">High Performance Optical File System</a></div>
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</div>
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</div>
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<img src="./deltaend.gif" alt="End of change" /></body>
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