When i typed the command "backup database" it mentioned
and then i checked the STATUS of the datafile 5
(look at the picture)
so i tried to recover ,it didn't work.
it told me that "ORA-00283: recovery session canceled due to errors ORA-01110: data file 5: '/u01/app/oracle/oradata/abc/abc.dbf' ORA-01157: cannot identify/lock data file 5 - see DBWR trace file ORA-01110: data file 5: '/u01/app/oracle/oradata/abc/abc.dbf' (datafile 7 is the same situation.)"
It reminded me that i once delected the document-abc under the graphic interface,which meant that i didn't use the command to delect the file.
so i tried to alter the datafile 5 and datafile 7.. it didn't work also.
how to alter the datafile 5 and 7? and backup database? thanks very much~！