Device requirement constraints on the size and number of SAP ASE devices.
Although some operating systems can designate an entire hard disk to use as a database device, Windows accepts only an operating system file (.dat file) as a database device.
When you install SAP ASE, the program creates a .dat file in the \data directory of the SAP ASE installation directory. To use a .dat file as a database device, you can either use the default d:\sap\data directory or create a device and a directory in which to store it.