When an OPEN or USE command includes no mnemonic space argument, Caché uses the default mnemonic for that device type. The File setting specifies the default mnemonic for sequential files.
The value n is a Caché routine name. ^%X364 is the default for sequential files. You can use this default, or reset it by changing the value of as needed. See the “Controlling Devices with Mnemonic Spaces” chapter in the Caché I/O Device Guide.
As described above.
On the page System Administration > Configuration > Device Settings > IO Settings, in the File row, enter a Caché routine name.