89 lines
5.8 KiB
HTML
89 lines
5.8 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE html
|
|
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
|
<html lang="en-us" xml:lang="en-us">
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<meta name="security" content="public" />
|
|
<meta name="Robots" content="index,follow" />
|
|
<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
|
|
<meta name="DC.Type" content="concept" />
|
|
<meta name="DC.Title" content="Input/output considerations for sequential-only processing" />
|
|
<meta name="abstract" content="The considerations apply for input/output operations on files when sequential-only processing is specified." />
|
|
<meta name="description" content="The considerations apply for input/output operations on files when sequential-only processing is specified." />
|
|
<meta name="DC.subject" content="input/output, sequential-only processing, input/output considerations" />
|
|
<meta name="keywords" content="input/output, sequential-only processing, input/output considerations" />
|
|
<meta name="DC.Relation" scheme="URI" content="rbafoseqop.htm" />
|
|
<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
|
|
<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
|
|
<meta name="DC.Format" content="XHTML" />
|
|
<meta name="DC.Identifier" content="rbafoicons" />
|
|
<meta name="DC.Language" content="en-us" />
|
|
<!-- All rights reserved. Licensed Materials Property of IBM -->
|
|
<!-- US Government Users Restricted Rights -->
|
|
<!-- Use, duplication or disclosure restricted by -->
|
|
<!-- GSA ADP Schedule Contract with IBM Corp. -->
|
|
<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
|
|
<link rel="stylesheet" type="text/css" href="./ic.css" />
|
|
<title>Input/output considerations for sequential-only processing</title>
|
|
</head>
|
|
<body id="rbafoicons"><a name="rbafoicons"><!-- --></a>
|
|
<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
|
|
<h1 class="topictitle1">Input/output considerations for sequential-only processing</h1>
|
|
<div><p>The considerations apply for input/output operations on files when
|
|
sequential-only processing is specified. </p>
|
|
<div class="p"> <ul><li>For input, your program receives one record at a time from the input buffer.
|
|
When all records in the input buffer are processed, the system automatically
|
|
reads the next set of records. <div class="note"><span class="notetitle">Note:</span> Changes made after records are read into
|
|
the input buffer are not reflected in the input buffer.</div>
|
|
</li>
|
|
<li>For output, your program must move one record at a time to the output
|
|
buffer. When the output buffer is full, the system automatically adds the
|
|
records to the database. <div class="note"><span class="notetitle">Note:</span> If you are using a journal, the entire buffer
|
|
is written to the journal at one time as if the entries had logically occurred
|
|
together. This journal processing occurs before the records are added to the
|
|
database.</div>
|
|
<p>If you use sequential-only processing for output, you might
|
|
not see all the changes made to the file as they occur. For example, if sequential-only
|
|
is specified for a file being used by PGMA, and PGMA is adding new records
|
|
to the file and the SEQONLY parameter was specified with 5 as the number of
|
|
records in the buffer, then only when the buffer is filled will the newly
|
|
added records be transferred to the database. In this example, only when the
|
|
fifth record was added, would the first five records be transferred to the
|
|
database, and be available for processing by other jobs in the system.</p>
|
|
<p>In
|
|
addition, if you use sequential-only processing for output, some additions
|
|
might not be made to the database if you do not handle the errors that can
|
|
occur when records are moved from the buffer to the database. For example,
|
|
assume that the buffer holds five records, and the third record in the buffer
|
|
had a key that was a duplicate of another record in the file and the file
|
|
was defined as a unique-key file. In this case, when the system transfers
|
|
the buffer to the database it would add the first two records and then get
|
|
a duplicate key error for the third. Because of this error, the third, fourth,
|
|
and fifth records in the buffer would <em>not</em> be added to the database.</p>
|
|
</li>
|
|
<li>The force-end-of-data function can be used for output operations to force
|
|
all records in the buffer to the database (except those records that would
|
|
cause a duplicate key in a file defined as having unique keys, as described
|
|
previously). The force-end-of-data function is only available in certain high-level
|
|
languages.</li>
|
|
<li>The number of records in a block will be changed to one if all of the
|
|
following conditions are true: <ul><li>The member was opened for output-only processing or sequential-only processing.</li>
|
|
<li>No override operations are in effect that have specified sequential-only
|
|
processing.</li>
|
|
<li>The file being opened is being extended because the increment number of
|
|
records was set to zero.</li>
|
|
<li>The number of bytes available in the file is less than the number of bytes
|
|
that fit into a block of records.</li>
|
|
</ul>
|
|
</li>
|
|
</ul>
|
|
</div>
|
|
</div>
|
|
<div>
|
|
<div class="familylinks">
|
|
<div class="parentlink"><strong>Parent topic:</strong> <a href="rbafoseqop.htm" title="If your program processes a database file sequentially for input only or output only, you might be able to improve performance using the sequential-only processing (SEQONLY) parameter on the Override with Database File (OVRDBF) or the Open Database File (OPNDBF) command.">Sequential-only processing of database files</a></div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html> |