96 lines
6.9 KiB
HTML
96 lines
6.9 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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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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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Stream file" />
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<meta name="abstract" content="A stream file is a randomly accessible sequence of bytes, with no further structure imposed by the system." />
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<meta name="description" content="A stream file is a randomly accessible sequence of bytes, with no further structure imposed by the system." />
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<meta name="DC.subject" content="stream file, comparison with record-oriented file, what is it?, why use, database file, comparison with stream file" />
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<meta name="keywords" content="stream file, comparison with record-oriented file, what is it?, why use, database file, comparison with stream file" />
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<meta name="DC.Relation" scheme="URI" content="rzaaxbasics.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzaaxudfsfs.htm" />
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<meta name="DC.Relation" scheme="URI" content="rzaaxstmpgm.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1999, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1999, 2006" />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Stream file</title>
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</head>
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<body id="rzaaxstmfile"><a name="rzaaxstmfile"><!-- --></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">Stream file</h1>
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<div><p>A <dfn class="term">stream file</dfn> is a randomly
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accessible sequence of bytes, with no further structure imposed by the system.</p>
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<p>The integrated file system provides support for storing and operating on
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information in the form of stream files. Documents that are stored in your
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server's folders are stream files. Other examples of stream files are PC files
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and the files in UNIX<sup>®</sup> systems. An integrated file system stream file
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is a system object that has an object type of *STMF.</p>
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<p>To better understand stream files, it is useful to compare them with iSeries™ database
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files. A database file is record-oriented; it has predefined subdivisions
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that consist of one or more fields that have specific characteristics, such
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as length and data type.</p>
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<div class="fignone"><span class="figcap">Figure 1. Comparison of a stream file and a record-oriented file</span><br /><img src="rv3n081.gif" alt="Comparison of a stream file and record-oriented file" /><br /></div>
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<p>Stream files and record-oriented files are structured differently, and
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this difference in structure affects how the files are used. The structure
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affects how an application is written to interact with the files and where
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each type of file is best used in an application. A record-oriented file,
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for example, is well suited for storing customer statistics such as name,
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address, and account balance. A record-oriented file allows these predefined
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fields to be individually accessed and manipulated, using the extensive programming
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facilities of your server. But a stream file is better suited for storing
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information such as a customer's picture, which is composed of a continuous
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string of bits representing variations in color. Stream files are particularly
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well suited for storing strings of data such as the text of a document, images,
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audio, and video.</p>
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<div class="p">A file has one of two format options: *TYPE1 stream file or *TYPE2 stream
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file. The file format depends on the release the file was created on, or if
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a file was created in a user-defined file system, the value that was specified
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for that file system.<div class="note"><span class="notetitle">Note:</span> The concept of *TYPE1
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and *TYPE2 stream files is different from the concept of *TYPE1 and *TYPE2
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directory formats. One does not relate to the other.</div>
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</div>
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<div class="section"><h4 class="sectiontitle">*TYPE1 stream files</h4><p>A *TYPE1
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stream file has the same format as stream files created on releases before OS/400<sup>®</sup> V4R4.</p>
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<p><img src="./delta.gif" alt="Start of change" />*TYPE1 stream file has a minimum size of 4096 bytes.
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*TYPE1 stream files have a maximum object size of approximately 128 GB (1
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GB equals approximately 1 073 741 824 bytes).<img src="./deltaend.gif" alt="End of change" /></p>
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</div>
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<div class="section"><h4 class="sectiontitle">*TYPE2 stream files</h4><p>A *TYPE2 stream file has high-performance
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file access.</p>
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<p>*TYPE2 stream files have a maximum
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object size of approximately 1 TB (1 TB equals approximately 1 099 511 627
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776 bytes) in the "root" (/), QOpenSys and user-defined file systems. Otherwise,
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the maximum is approximately 256 GB. It is also capable of memory mapping,
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as well as the ability to specify an attribute to optimize main storage allocation.
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All files created with OS/400 V4R4 and newer systems are *TYPE2 stream files,
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unless they were created in a user-defined file system that specified a file
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format of *TYPE1.</p>
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<div class="note"><span class="notetitle">Note:</span> Any files larger than 256
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GB cannot be saved or restored to systems before <span class="keyword">i5/OS™</span> V5R3.</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="rzaaxbasics.htm" title="This topic introduces the basic concepts of integrated file system, such as directory, link, path name, stream file, name continuity, extended attributes, and scanning support.">Integrated file system concepts</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="rzaaxudfsfs.htm" title="The user-defined file systems (UDFSs) reside on the auxiliary storage pool (ASP) or independent auxiliary storage pool (ASP) of your choice. You create and manage these file systems.">User-defined file systems (UDFSs)</a></div>
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<div><a href="rzaaxstmpgm.htm" title="If you are familiar with operating on database files using record-oriented facilities such as data description specifications (DDS), you may find some fundamental differences in the way you operate on stream files.">Copy data between stream files and database files</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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