Costs and limitations of geographic mirroring

To configure geographic mirroring between two sites, the following items are required:

At least one iSeries™ server at each site.
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.
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.
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 Communications requirements for more information.

Limitations of geographic mirroring include these constraints:

When geographic mirroring is being performed, you cannot access the mirror copy; this ensures that the data integrity of the mirror copy is maintained.
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.
Synchronization can be a lengthy process, especially if geographic mirroring was suspended without tracking.