ORA-01654: Unable to extend index %s.%s by %s in tablespace %s

The tablespace the index is residing in is unable to extend.

There is not enough space left either due to the datafiles being full, autoextend which is not set at datafile level or due to a disk which's full.

You'll have to check the size of the datafiles attached to the tablespace and check whether they can autoextend or not.

select file_name, bytes, autoextensible, maxbytes
from dba_data_files
where tablespace_name='TABLESPACE_NAME'

Either add more datafiles to the tablespace, set the autoextensible flag or enlarge the datafile(s).

To add more space to a file issue following command:

alter database datafile 'C:\ORACLE\ORADATA\IDX01.DBF' resize 1000m;

To turn on the autoextend feature on a datafile use following command:

alter database datafile 'C:\ORACLE\ORADATA\IDX01.DBF' autoextend on next 100m maxsize 2000m;

To add a new datafile to the tablespace use following command:

alter tablespace IDX add datafile 'C:\ORACLE\ORADATA\IDX02.DBF' size 100m autoextend on next 100m maxsize 2000m;