You cannot alter an existing directory access server: you must drop the existing directory access server using a DROP SERVER statement, and then create a new one.
Open the Directory Access Servers folder for the database.
Select the directory access server, and then choose Edit > Delete.
Execute a DROP SERVER statement.
For example:
DROP SERVER my_directory_server;
Use the DROP TABLE statement to drop a proxy table used by the directory access server.
Open the Directory Access Servers folder for the database.
In the right pane, click the Proxy Tables tab.
Select the proxy table, and then choose Edit > Delete.
Execute a DROP TABLE statement.
For example:
DROP TABLE my_files;