Customer Data Upgrade

Hi,

We are migrating customer data from legacy system to Dynamics AX 2012 R3 through a txt file using Customer's entity.

We are getting an error msg as

"Unable to return Dimension Attribute value for %1 (given customer)".

Could someone please help me sort out this error or guide me the pre-requisite processes to be done before importing data through Customer entity so that the error doesn't arise.

Thanks,

Lakshmi