7A.
1. alter user scott default tablespace data;
6. alter database archivelog;
7. archive log list;
8. alter database open;
12. archive log list
14. select sum(sal) from scott.emp;
18. set autorecovery on;

7B.
4. alter database datafile 'filename' offline;
5. recover tablespace data;
        alter database datafile 'filename' online;

7C.
7. recover tablespace data;

7D.
3. ALTER DATABASE BACKUP CONTROLFILE TO 'filename.bkp';
ALTER DATABASE BACKUP CONTROLFILE TO TRACE;
6.alter system swithc logifle;