The DEFAULT Connection Specification

Instead of specifying an explicit database environment, you can use the DEFAULT keyword to request a default connection to a default database server. The default database server can be local or remote. To designate the default database server, set its name in the ONEDB_SERVER environment variable. This option of CONNECT does not open a database.

If the CONNECT TO DEFAULT statement succeeds, you must use the DATABASE statement or the CREATE DATABASE statement to open or create a database in the default database environment.