In DB02 transaction of my BW production server i'm getting following entry on Database tab:

  Name         DEFAULT

DB system:        ORA

Size:                    45,83 GB                       Total size:                 156,25 GB

Free Size:                9,16 GB                       Total free size:            119,58 GB

Used:                       80 %                        Total used:                     23 %

Size: 45,83 GB v --> the size is currently allocated in file system

Total size: 156,25 GB the size is MAX calculeted (Your DB can grow up tothis size in file system) because the AUTOEXTEND are turned ON.

Free Size: 9,16 GB --> really free space in DB now

Total free size: 119,58 GB Free size  --> total free autoextendable size ...

Used: 80 % --> 45,83 DB, free 9,16 (20%)  --> used 80% (36,67)

Total used: 23 % --> Total (inc AUTOEXTEND) size are 156,25 (100%) --> used 36,67 == 23%