If you omit the size parameter in the on clause, SAP ASE creates the database with a default amount of space.
This amount is the larger of the sizes specified by the default database size configuration parameter and the model database.
The smallest database you can create is the size of the model database, which is determined by your installation’s logical page size. To increase the minimum size of a database, use alter database to enlarge the model database. You can also use the default database size configuration parameter to determine the default database size. See System Administration Guide: Volume 1 > Setting Configuration Paramters.
If you omit the on clause, the database is created as the default size, as described above. The space is allocated in alphabetical order by database device name, from the default database devices specified in master..sysdevices.
select name from sysdevices where status & 1 = 1 order by name
sp_helpdevice also displays “default disk” as part of the description of database devices.