During a set of incremental restores, RESTORE creates and drops dbspaces as needed to match what was done during the period of operation encompassed by the restores.
For example, assume that you make a full backup of a database, then add a dbspace to that database, and then do an incremental backup after adding the dbspace. When you restore from these backups, RESTORE creates a file for the new dbspace, at the start of the incremental restore. Similarly, if you drop a dbspace, it is dropped during the restore, although the actual file is not removed.
Note that the file_name column in the SYSFILE system table for the SYSTEM dbspace is not updated during a restore. For the SYSTEM dbspace, the file_name column always reflects the name when the database was created. The file name of the SYSTEM dbspace is the name of the database file.