The alter table command allows column types to be modified. With the Adaptive Server Enterprise version 12.5, a column’s type can be modified to and from Unicode datatypes. If the command operates upon a proxy table, the command is reconstructed and forwarded to the remote server that owns the actual table. If the remote server (or DirectConnect) cannot process the command, an error is expected, and the Adaptive Server Enterprise command will be aborted.
If traceflag 11221 is ON, then the alter table command does not get forwarded to a remote server; adding, deleting or modifying columns is only done locally on the proxy table.