v$backup:- it is used to determine which files are in backup mode. when an
alter tablespace begin backup command
is issued the status changes to active
v$datafile_header:- it is used to get information about datafiles that are in backup mode can also be derived by quering. when an alter tablespace begin backup commands is issued. the value in the fuzzy column for the tablespace datafile changes to " yes " to indicate that the corresponding files are in backup mode.