Check online and offline datafiles

select a.file#, b.name ts_name from v$datafile a, v$tablespace b where a.ts#=b.ts# and b.name not in ('SYSTEM','SYSAUX') and a.status='ONLINE'




select a.file# from v$datafile a, v$tablespace b where a.ts#=b.ts# and b.name  in ('UNDOTBS1','UNDOTBS2');




select a.file# from v$datafile a, v$tablespace b where a.ts#=b.ts# and b.name not in ('SYSTEM','SYSAUX') and a.status='OFFLINE'