If you are opening an existing file, most file systems linked into the run time system are searched for the named file. If, however, you are creating a new file, you must tell the run time system which file system to use. You accomplish this with the following ACUFH configuration file variable:
DEFAULT_HOST filesystem
This variable designates the file system used for newly created files that are not individually assigned. If this variable is not given a value, the EXTFH file system is used.
Examples
DEFAULT_HOST DB2
means that all new files are be DB2 files unless individually assigned to another file system.
DEFAULT_HOST ORACLE
means that all new files are be Oracle files unless individually assigned to another file system.