USER_FREE_SPACE

Free extents in tablespaces accessible to the user

Columns
   ___________________________
 
   TABLESPACE_NAME
      Name of the tablespace containing the extent
   FILE_ID
      ID number of the file containing the extent
   BLOCK_ID
      Starting block number of the extent
   BYTES
      Size of the extent in bytes
   BLOCKS
      Size of the extent in ORACLE blocks
   RELATIVE_FNO
      Relative number of the file containing the extent