Solution

When you create a synonym that contains NVARCHAR(max), the column is described  as:

                      USAGE=TX50, ACTUAL=TX
Microsoft Azure SQL Data Warehouse has a 2GB limit on NVARCHAR(max) data.
The WebFOCUS MS Azure SQL Data Warehouse adapter does not have a size limit for TX columns, therefore, NVARCHAR(max) has no limit in the adapter, only the limit defined by Microsoft.
For NVARCHAR(n), create synonym describes the column as:

                      USAGE=AnV, ACTUAL= AnV    
The limit is n=32765, so anything above 32765 will be truncated.
          
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