ibm-information-center/dist/eclipse/plugins/i5OS.ic.rzam4_5.4.0.1/rzam4highperfofs.htm

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<title>High Performance Optical File System</title>
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<h1 class="topictitle1">High Performance Optical File System</h1>
<div><p>High performance optical file system (HPOFS) is an IBM-developed
media format architecture available to use when initializing optical media
on the i5/OS™.</p>
<p>i5/OS uses
the WORM-based version of HPOFS. This media format is designed (and required)
for WORM media, but you can use it (and it is the default) when initializing
erasable optical media. HPOFS is a WORM media format. You can write each sector
of the media only once when creating and updating files and directories. This
unique characteristic of never rewriting the same sector allows all previous
versions of every file to remain on the media. One drawback of this is that
media consumption continues to grow as you update and even delete files. </p>
<p>This section contains detailed information on the i5/OS implementation of HPOFS for directly-attached
optical media libraries. This section does not address HPOFS characteristics
for LAN-attached optical media libraries.</p>
<p>Detailed information on the i5/OS implementation of HPOFS for directly
attached optical media libraries is available in the CL command support for
media formats.</p>
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<ul class="ullinks">
<li class="ulchildlink"><strong><a href="rzam4hpofsvoldirfile.htm">Volume, directory, and file names for HPOFS</a></strong><br />
HPOFS volume identifiers can be a maximum of 32 characters and must contain only alphabetic characters (A through Z), numeric characters (0 through 9), a hyphen (-), or a period (.).</li>
<li class="ulchildlink"><strong><a href="rzam4spcreclaim.htm">Space reclaim</a></strong><br />
You can update or delete files even though HPOFS is a write-once read-many (WORM) media format.</li>
<li class="ulchildlink"><strong><a href="rzam4hpofsproginter.htm">Programming interfaces (HPOFS)</a></strong><br />
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).</li>
<li class="ulchildlink"><strong><a href="rzam4hpofsdirstructperf.htm">Directory structure and performance (HPOFS)</a></strong><br />
HPOFS volumes have a dual directory structure to access files. Both a hash and hierarchical structure exist to provide a primary and secondary path to the file data. If the primary directory structure becomes damaged, the secondary path is used.</li>
<li class="ulchildlink"><strong><a href="rzam4mediainterchange.htm">Media interchange between LAN and direct attach libraries</a></strong><br />
This topic lists how HPOFS formatted optical media created in a LAN-attached optical library can be accessed.</li>
</ul>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzam4optmedfrmat.htm" title="i5/OS provides support for several optical media types and media formats.">Optical media formats</a></div>
</div>
<div class="relconcepts"><strong>Related concepts</strong><br />
<div><a href="rzam4clcomsupfmts.htm" title="This topic provides information on using i5/OS commands to save and restore data and some of the restrictions for the ISO 9660, High Performance Optical File System (HPOFS), and universal disk format (UDF) media formats.">CL command support for media formats</a></div>
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