ORA-01654: unable to extend index

IF you are using ASM then you can add with below comment

you can run below command to get size of datafile

SELECT
    file_name,
    bytes / 1024 / 1024 mb
FROM
    dba_data_files
WHERE
    tablespace_name = 'APP_DATA'
ORDER BY
    file_name;


FILE_NAME mb
------------------------------------------------------------ -------
+DATA/SID/datafile/app_data.dbf 20000
+DATA/SID/datafile/app_data.dbf 28100

Resizing and adding

+DATA/path/indx_operational_00.dbf

alter database datafile '+DATA/path/indx_operational_00.dbf' resize 3000m;

You are out of disk space.

Increase your TABLESPACE:

ALTER TABLESPACE DABUAT_TBLSP
ADD DATAFILE 'C:\FolderWithPlentyOfSpace\DABUAT_TBLSP001.DBF' 
SIZE 4M
AUTOEXTEND ON NEXT 4M
MAXSIZE 64G;

-- Put your own size parameters here