Some important queries.........!

sql> select file_name , tablespace_name from dba_datafile_files where tablespace_name like
'%HRD%';

sql> select open_mode from v$database;

sql> desc v$database;

sql> select log_mode from v$database;

sql> select name from v$tablespace;

sql> select name from v$datafile;

sql> select name from v$tablespace;

sql> select count(*) from v$tablespaces;


Bakup

sql> alter tablespace HRD begin backup ;
copy the datafile to the backup location
sql> alter tablespace HRD end backup;

sql> select open_mode from v$datafile;

sql> alter database open reset logs;



Tablespace Offline:

sql> alter database datafile '/u01/appsmode/jet/oradata/data/HRD01.dbf' offline;


exit
copy the datafile from backup

recover datafile 7;

sql> alter database datafile '/u01/appsmode1/jet/oradata/data/hrd01.dbf' online;