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<h1 class="topictitle1">Costs and limitations of geographic mirroring</h1>
<div><div class="section"><h4 class="sectiontitle">Costs</h4><p>To configure geographic mirroring between
two sites, the following items are required:</p>
<div class="p"><ul><li>At least one iSeries™ server
at each site. </li>
<li>Sufficient CPU support for the additional CPU capacity required
for geographic mirroring. A fraction of a processor for a partition supporting
geographic mirroring is not adequate.</li>
<li>Sufficient disk units at each site for the production and
the mirror copy of the geographically mirrored independent disk pools. To
avoid disk unit contention, use separate input/output adapters for the production
copy on its node and for the mirror copy on its node.</li>
<li>One TCP/IP connection from each node should
connect the two sites. A second TCP/IP connection is strongly recommended
to provide redundancy and better performance. You may configure up to four
TCP/IP connections. See <a href="rzalycommunications.htm">Communications requirements</a> for
more information.</li>
</ul>
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<div class="section"><h4 class="sectiontitle">Limitations</h4><div class="p">Limitations
of geographic mirroring include these constraints:<ul><li>When geographic mirroring is being performed, you cannot access the mirror
copy; this ensures that the data integrity of the mirror copy is maintained.</li>
<li>If you detach the mirror copy to perform a save operation, to perform
data mining, or to create reports, you must reattach the mirror copy to resume
geographic mirroring. The mirror copy must be synchronized with the production
copy after it is reattached. Synchronization can be a lengthy process.</li>
<li>Synchronization can be a lengthy process, especially if geographic mirroring
was suspended without tracking.</li>
</ul>
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzalygeographicmirror.htm">Geographic mirroring</a></div>
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