I can not copy database MongoDB

I created a mongo cluster in ubuntu and run the copy in the sharding with a small database, everything works fine.

The problem is that when I try to copy a database 300gb, is not getting done. The host where I have the mongos instance, run the following:

db.runCommand ({copydb: 1, fromdb: "tranches" todb: "tranches" fromhost: "mongoserver: 27025"})

And the following appears:

{ "code": 13398,"ok": 0,"errmsg": "exception: cant copy to sharded DB" }

What could be the problem ?, any idea for the problem?.