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<h1 class="topictitle1">Typical use of data queues</h1>
<div><p>A data queue is a powerful program-to-program interface. Programmers
who are familiar with programming on the iSeries™ servers are accustomed to using
queues. Data queues simply represent a method that is used to pass information
to another program.</p>
<p>Because this interface does not require communications programming, use
it either for synchronous or for asynchronous (disconnected) processing.</p>
<p>Develop host applications and PC applications by using any supported language.
For example, a host application could use RPG while a PC application might
use C++. The queue is there to obtain input from one side and to pass input
to the other.</p>
<p>The following example shows how data queues might be used: </p>
<ul><li>A PC user might take telephone orders all day, and key each order into
a program, while the program places each request on iSeries data queue.</li>
<li>A partner program (either a PC program or an iSeries program) monitors the data queue
and pulls information from queue. This partner program could be simultaneously
running, or started after peak user hours.</li>
<li>It may or may not return input to the initiating PC program, or it may
place something on the queue for another PC or iSeries program.</li>
<li>Eventually the order is filled, the customer is billed, the inventory
records are updated, and information is placed on the queue for the PC application
to direct a PC user to call the customer with an expected ship date.</li>
</ul>
<div class="section"><h4 class="sectiontitle">Objects</h4><p>An application that uses the data queue
function uses four <strong>objects</strong>. Each of these objects is identified to
the application through a handle. The objects are: </p>
<dl><dt class="dlterm">Queue object:</dt>
<dd>This object represents the iSeries data queue.</dd>
<dt class="dlterm">Attribute:</dt>
<dd>This object describes the iSeries data queue.</dd>
<dt class="dlterm">Data:</dt>
<dd>Use these objects to write records to, and to read records from, the iSeries data
queue.</dd>
<dt class="dlterm">Read object:</dt>
<dd>Use this object only with the asynchronous read APIs. It uniquely identifies
a request to read a record from the iSeries data queue. This handle is used
on subsequent calls to check if the data has been returned. See the <a href="rzaikcwbdqasyncread.htm#cwbdq_asyncread">cwbDQ_AsyncRead</a> API
for more information.</dd>
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaikappdq.htm" title="Use iSeries Access for Windows Data Queues application programming interfaces (APIs) to provide easy access to iSeries data queues. Data queues allow you to create client/server applications that do not require the use of communications APIs.">iSeries Access for Windows Data Queues APIs</a></div>
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