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<h1 class="topictitle1"><span class="keyword">iSeries server</span> and <span class="keyword">System/36</span> DDM differences</h1>
<div><p>This topic consists of a list of differences between the <span class="keyword">iSeries™ server</span> and <span class="keyword">System/36™</span>.</p>
<div class="section"> <ul><li>The network resource directory (NRD) procedures are not supported on the <span class="keyword">iSeries server</span>. <ul><li>The <span class="keyword">System/36</span> NRD used one
or more libraries containing DDM files on the <span class="keyword">iSeries server</span>.
One <span class="keyword">System/36</span> NRD entry is equivalent
to one DDM file on the <span class="keyword">iSeries server</span>.
<ul><li>Use the <span class="cmdname">Work with DDM Files (WRKDDMF)</span> command in place
of the EDITNRD and DELNRD procedures.</li>
<li>Use the <span class="cmdname">Display DDM Files (DSPDDMF)</span> command in place
of the LISTNRD procedure.</li>
<li>Use the<span class="cmdname"> Restore Object (RSTOBJ)</span> command in place of
the RESTNRD procedure.</li>
<li>Use the <span class="cmdname">Save Object (SAVOBJ)</span> command in place of the
SAVNRD procedure.</li>
</ul>
</li>
<li>If an NRD entry on the <span class="keyword">System/36</span> refers
to a remote file, and a SAVE or RESTORE procedure is requested, the <span class="keyword">System/36</span> saves or restores the data
of the remote file. The <span class="keyword">iSeries</span> <span class="cmdname">Save
Object (SAVOBJ)</span> or <span class="cmdname">Restore Object (RSTOBJ)</span> command
saves or restores only the definition of the DDM file, not the remote data.</li>
<li>When using date-differentiated files on the <span class="keyword">System/36</span>,
the most current file is selected. When running from a <span class="keyword">System/36</span> to
an <span class="keyword">iSeries server</span>, the NRD entry
must specify a member name of *LAST to access the last member of the database
file, which is the file with the most recent date. If no member name is specified,
*FIRST is used.</li>
</ul>
</li>
<li>The remote label in the NRD on a <span class="keyword">System/36</span> source
must be in the syntax required by the target server. </li>
<li>The number of records allocated for a file differs between the <span class="keyword">System/36</span> and the <span class="keyword">iSeries server</span>.
File space allocation on the <span class="keyword">System/36</span> is
in block units (2560 bytes) while on the <span class="keyword">iSeries server</span>,
file space allocation is by number of records. For example, if a user asks
for a sequential file capable of storing ten 100-byte records, the <span class="keyword">System/36</span> allocates 1 block of file space
(2560 bytes), and uses as much of the file space as possible (2500 bytes),
giving the user twenty-five 100-byte records. <p>The <span class="keyword">iSeries server</span> allocates
exactly 10 records. If the user took advantage of this allocation method on
the <span class="keyword">System/36</span>, the file (nonextendable)
created using DDM on the <span class="keyword">iSeries server</span> might
be too small.</p>
</li>
<li>The DDM <span class="cmdname">Change End-of-File (CHGEOF)</span> command used on
the <span class="keyword">System/36</span> is not supported
on the <span class="keyword">iSeries server</span>.</li>
<li>The <span class="keyword">iSeries server</span> does not support
writing over data on the <span class="cmdname">Delete File (DLTF)</span> command. If
an <span class="keyword">iSeries</span> user accessing a <span class="keyword">System/36</span> wants to overwrite the data,
an application program must be written on the <span class="keyword">iSeries server</span>,
or the user must access the target <span class="keyword">System/36</span> and
perform the delete operation with the erase operation.</li>
<li>A <span class="keyword">System/36</span> source server
cannot create direct files on an <span class="keyword">iSeries</span> target
server that are nondelete-capable. The <span class="keyword">iSeries server</span> does
not support files that are nondelete-capable for all file organizations.</li>
<li>The <span class="keyword">System/36</span> does not allow
a record with hex FF in the first byte to be inserted into a delete-capable
file. The <span class="keyword">iSeries server</span> allows this.</li>
<li>When running <span class="keyword">System/36</span> applications
to another <span class="keyword">System/36</span>, the application
waits indefinitely for the resource to become available. When running <span class="keyword">System/36</span> applications to or from an <span class="keyword">iSeries server</span>, these applications might result
in time-outs while waiting for a resource to become available.</li>
<li>Direct files are extendable on the <span class="keyword">System/36</span> but
not on the <span class="keyword">iSeries server</span>. If a direct
file is created on the <span class="keyword">iSeries server</span> as
extendable, the file is allocated with three extents, but is never extended
beyond the initial size plus three extents.</li>
<li>The <span class="keyword">System/36</span> relay function
is <em>not</em> supported whenever one of the servers in the network along the
path from the source server to the target server is not a <span class="keyword">System/36</span>.
The <span class="keyword">iSeries server</span> <em>never</em> supports
the relay function; Advanced Peer-to-Peer Networking (APPN) must be used.</li>
<li>Key fields on the <span class="keyword">System/36</span> are
considered to be strictly character fields. The <span class="keyword">System/36</span> does
not recognize a key field as being packed or zoned. Unexpected results might
occur if source <span class="keyword">iSeries</span> application
programs refer to packed fields within a <span class="keyword">System/36</span> file.
Because of the way packed numbers are stored and the fact that the <span class="keyword">System/36</span> does not recognize key fields
as packed on relative keyed operations, records might be returned in a different
order than expected or no record might be found when one is expected. <p>As
an example, the ILE RPG SETLL statement might fail unexpectedly with record
not found or might select a record other than the record expected when using
packed fields to a <span class="keyword">System/36</span> file.
Only character and unsigned numeric fields should be used as key fields.</p>
</li>
</ul>
</div>
</div>
<div>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="rbae5dif.htm" title="This topic describes the DDM differences between iSeries server and System/36, and iSeries server and System/38.">Use DDM on the iSeries server versus other IBM systems</a></div>
</div>
<div class="relconcepts"><strong>Related concepts</strong><br />
<div><a href="../rzahg/rzahgupgrademigration.htm">Migration</a></div>
</div>
<div class="relref"><strong>Related reference</strong><br />
<div><a href="rbae5namecon.htm" title="The rules for specifying the name of a DDM file (on the local iSeries server) are the same as for any other file type on an iSeries server. The rules, however, for specifying the name of a remote file depend on the type of target server.">Rules for specifying target server file names for DDM</a></div>
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