While doing merge replication in sql sever between two machine(both on world IP) I facing an error:

copying the data to another server, this error is shown -

The process could not make a generation at the 'Subscriber'.
(Source: Merge Replication Provider (Agent); Error number:
Cannot insert the value NULL into column 'nicknames', table
'NasscomData.dbo.MSmerge_genhistory'; column does not allow nulls.
INSERT fails.
(Source: (Data source); Error number: 515)


Anil Sharma