"corrupted" Oracle 11g datafile prohibits all further action on db

db issue: Both databases. Unused datafile undotbs2 is corrupt.
select df.tablespace_name "Tablespace",
totalusedspace "Used MB",
(df.totalspace - tu.totalusedspace) "Free MB",
df.totalspace "Total MB",
round(100 * ( (df.totalspace - tu.totalusedspace)/ df.totalspace))
"Pct. Free"
from
(select tablespace_name,
round(sum(bytes) / 1048576) TotalSpace
from dba_data_files
group by tablespace_name) df,
(select round(sum(bytes)/(1024*1024)) totalusedspace, tablespace_name
from dba_segments
group by tablespace_name) tu
where df.tablespace_name = tu.tablespace_name ;

ORA-01115: IO error reading block from file (block # )
ORA-01110: data file 63: '/oracledb/data/vzdaadb/undotbs2.dbf'
ORA-27072: File I/O error
Additional information: 4
Additional information: 2
01115. 00000 - "IO error reading block from file %s (block # %s)"
*Cause: Device on which the file resides is probably offline
*Action: Restore access to the device

select * from dba_data_files;

ORA-01115: IO error reading block from file (block # )
ORA-01110: data file 63: '/oracledb/data/vzdaadb/undotbs2.dbf'
ORA-27072: File I/O error
Additional information: 4
Additional information: 2
01115. 00000 - "IO error reading block from file %s (block # %s)"
*Cause: Device on which the file resides is probably offline
*Action: Restore access to the device

Want to get rid of corrupt undotbs2 datafile and clean up the other added but no longer being written to undo datafiles.
(RMAN does not find anything to fix so it has been of little help here.)

Currently have all pointed to undotbs101 and probably added it with autoextend so maybe we can get rid of all the others.

But cannot backup database with undotbs2 in a corrupted mode.

I must have really screwed something up when adding it.