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On completion of load, check for any errors during load by selecting the Events Tab and Errors box which will display the errors. Selecting the error will display the error detail and which object failed. In sample migration, 2 phone devices failed to load as they were duplicates of existing MAC addresses. To resolve - there will be a link within the error detail linking to object detail (can also be accessed using Object->Browse from menu then finding the detail of the offending object) where the error can be corrected and load process restarted by selecting Restart Execution Process
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On rectification of issues and restart all objects loads OK
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