ibm-information-center/dist/eclipse/plugins/i5OS.ic.rzalf_5.4.0.1/rzalfwhenuseful.htm

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<h1 class="topictitle1">When is <span class="keyword">i5/OS</span> PASE
a useful option for application development?</h1>
<div><p>You can use API analysis to determine whether an application is
suitable for <span class="keyword">i5/OS™</span> PASE. <span class="keyword">i5/OS</span> PASE is not the best solution
under some circumstances.</p>
<p><span class="keyword">i5/OS</span> PASE provides
considerable flexibility when you are deciding how to port your AIX<sup>®</sup> applications
to the iSeries™ server.
Of course, <span class="keyword">i5/OS</span> PASE is
only one option of several from which you can choose.</p>
<div class="section"><h4 class="sectiontitle">API analysis</h4><p>Your starting point for determining
whether an application is suitable for <span class="keyword">i5/OS</span> PASE
is an analysis of the application: the APIs, libraries, and utilities that
it uses and how effectively it will run on <span class="keyword">i5/OS</span>.
The IBM<sup>®</sup> Virtual
Innovation Center for Hardware offers help in this area with the API Analysis
Tool, a free porting assessment tool that analyzes your application and describes
potential stumbling blocks. For more information about how the analysis tool
fits into the procedures for porting applications to <span class="keyword">i5/OS</span> PASE,
see the <a href="rzalfpreparing.htm">Prepare programs to run in i5/OS PASE</a> topic.</p>
</div>
<div class="section"><h4 class="sectiontitle">Characteristics of a potential <span class="keyword">i5/OS</span> PASE
application</h4><p>Here are some useful guidelines that you might consider
when making the decision whether to use <span class="keyword">i5/OS</span> PASE:</p>
<ul><li><strong>Is the AIX application
highly compute-intensive?</strong> <p><span class="keyword">i5/OS</span> PASE
provides a good environment for running computation-intensive applications
on iSeries servers
by providing highly optimized math libraries.</p>
</li>
<li><strong>Does the application rely heavily on functions that are supported only
in <span class="keyword">i5/OS</span> PASE (or only
partially supported in ILE), such as fork(), X Window System, or pseudo-terminal
(PTY) support?</strong> <p><span class="keyword">i5/OS</span> PASE
provides support for fork() and exec(), which do not currently exist on the <span class="keyword">i5/OS</span> system (except through spawn(),
which incorporates the fork() function with the exec() function).</p>
</li>
<li><strong>Does the application use a complicated AIX system-based build process or testing
environment?</strong> <p><span class="keyword">i5/OS</span> PASE
lets you use AIX system-based
build processes, which are especially useful when you have an existing, complicated
process that is not readily transferred onto a new operating system.</p>
</li>
<li><strong>Does the application have dependencies on an ASCII character set?</strong><p><span class="keyword">i5/OS</span> PASE
provides good support for applications with these needs. </p>
</li>
<li><strong>Does the application do a lot of pointer manipulation, or does it convert
(cast) integers to pointers?</strong><p><span class="keyword">i5/OS</span> PASE
supports both 32- and 64-bit AIX addressing models with low performance cost and the
ability to convert integers to pointers.</p>
</li>
</ul>
</div>
<div class="section"><h4 class="sectiontitle">When <span class="keyword">i5/OS</span> PASE
might not be the best solution</h4><p><span class="keyword">i5/OS</span> PASE
is generally not a good choice for code that provides a large number of callable
interfaces that must be called from ILE and that has any of the following
characteristics:</p>
<ul><li>Code that needs higher performance call and return than provided by either
starting or ending <span class="keyword">i5/OS</span> PASE
on each call or by calling an <span class="keyword">i5/OS</span> PASE
procedure in an already-active <span class="keyword">i5/OS</span> PASE
program (using the Qp2CallPase API).</li>
<li>Code that needs to share memory or namespace between an ILE caller and
the library code. An <span class="keyword">i5/OS</span> PASE
program does not implicitly share memory or namespace with ILE code that called
it. (However, ILE code that is called from <span class="keyword">i5/OS</span> PASE
can share or use <span class="keyword">i5/OS</span> PASE
memory.)</li>
</ul>
</div>
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<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzalfgetstart.htm" title="i5/OS Portable Application Solutions Environment (i5/OS PASE) enables you to run many of your AIX application binaries on i5/OS with little or no change, and effectively expands your platform solution portfolio.">Get started with i5/OS PASE</a></div>
</div>
<div class="relinfo"><strong>Related information</strong><br />
<div><a href="http://www.ibm.com/servers/enable/site/porting/iseries/overview/apitool.html" target="_blank">API Analysis Tool</a></div>
<div><a href="http://www.ibm.com/servers/enable/site/porting/iseries/" target="_blank">IBM Virtual Innovation Center for Hardware</a></div>
</div>
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