Oracle Script: fix the index with status unusable

ORA-01502: index 'xxx. xxxx' or partition of such index is in unusable state. Solution: Log On With DBA and run the following script.

1. -- Log On with the DBA permission and execute
2. -- Fix all indexes in the UNUSABLE status and rebuild them.
3. Declare
4. -- Cursor pointing to the index of all UNUSABLE states
5. CursorCIs
6. SelectIndex_name, owner
7. FromDba_indexes
8. WhereStatus ='Unusable';
10. Owner dba_indexes.owner % type;
11. Index_name dba_indexes.index_name % type;
12. Begin
13. OpenC;
14. Loop
15. FetchCIntoIndex_name, owner;
16. ExitWhenC % notfound;
18. ExecuteImmediate'Alter Index'| Owner |'.'| Index_name |'Rebuilt';
19. EndLoop;
20. CloseC;
21. End;

Thought 1: Why does a normal operation cause an index to be unusable?

Thinking 2: how to solve this problem without logging on to the DBA? (I tried to get all the indexes of the current user from the user_indexes table, but they cannot be edited)