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<title>Using User Space APIs</title>
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<h2>Using User Space APIs</h2>
<p><strong>User spaces</strong> are objects that consist of a collection of
bytes used for storing user-defined information. They are permanent objects
that are located in either the system domain or the user domain. They have an
object type of *USRSPC and a maximum size of 16MB. You can save and restore
user spaces to other systems. If, however, the user spaces contain pointers,
you cannot restore the pointers even if you want to restore them to the same
system.</p>
<p> You can use the user space APIs to:</p>
<ul>
<li>Create user spaces to be used by list APIs to generate lists of data.</li>
<li>Store pointers.</li>
<li>Store large amounts of data. You can create a user space as large as 16
megabytes. You cannot create a data area larger than 2000 bytes.</li>
<li>Save information in user space objects, and save and restore the object
with the information in it using CL commands.</li>
<li>Pass data from job to job or from system to system.</li>
</ul>
<p> <strong>Note:</strong> If the allow user domain (QALWUSRDMN) system value
contains only the QTEMP library, you can use only the user space APIs to create and manipulate
user domain spaces in library QTEMP. You cannot use the Retrieve Pointer to User
Space API.
</p>
<p><img src="delta.gif" alt="Start of change">The performance benefits of using optimally aligned spaces may vary over time, so creating a user space with optimum alignment is highly recommended, even if an application does not experience a performance benefit from using an optimally aligned user space on one particular release.<img src="deltaend.gif" alt="End of change">
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