DBA_DATA_FILES describes database files.

Column Datatype NULL Description
FILE_NAME VARCHAR2(513)   Name of the database file
FILE_ID NUMBER NOT NULL File identifier number of the database file
TABLESPACE_NAME VARCHAR2(30) NOT NULL Name of the tablespace to which the file belongs
BYTES NUMBER   Size of the file in bytes
BLOCKS NUMBER NOT NULL Size of the file in Oracle blocks
STATUS VARCHAR2(9)   File status: AVAILABLE or INVALID (INVALID means that the file number is not in use, for example, a file in a tablespace that was dropped)
RELATIVE_FNO NUMBER   Relative file number
AUTOEXTENSIBLE VARCHAR2(3)   Autoextensible indicator
MAXBYTES NUMBER   Maximum file size in bytes
MAXBLOCKS NUMBER   Maximum file size in blocks
INCREMENT_BY NUMBER   Number of Oracle blocks used as autoextension increment
USER_BYTES NUMBER   The size of the file available for user data. The actual size of the file minus the USER_BYTES value is used to store file related metadata.
USER_BLOCKS NUMBER   Number of blocks which can be used by the data
ONLINE_STATUS VARCHAR2(7)   Online status of the file: