The existing solution attempts failed:

1. The table space is insufficient.

2. Rebuild the index or merge the index

Solution 3: delete the index directly without a large amount of data

drop index index-name;

There may be table locking problems:
step one:

 select  session_id from v$locked_object;

Step two:

 select  sid，serial#,username,osuser from v$session where sid = 545;

Step three:

alter system kill session '545,36043';

#The Sid and session here need to be modified according to their own requirements