Error in concatenation of `LISTAGG` function[Not a duplicate question]

Question

I have the below table(run on SQL Commander) and procedure(run on procedure window). Im am trying to run on DB-VISUALIZER.

CREATE TABLE tempt( "set" VARCHAR2(1), "level" VARCHAR2(1), category VARCHAR2(3), value INT );

INSERT INTO tempt
SELECT 'A', 'Z', 'ABC', 847549 FROM dual UNION ALL
SELECT 'A', 'Y', 'ABC', 955808 FROM dual UNION ALL
SELECT 'A', 'X', 'ABC', 983462 FROM dual UNION ALL
SELECT 'A', 'Z', 'GHI', 762369 FROM dual UNION ALL
SELECT 'A', 'Y', 'DEF', 615863 FROM dual UNION ALL
SELECT 'A', 'X', 'DEF', 474257 FROM dual UNION ALL
SELECT 'B', 'Z', 'ABC', 959843 FROM dual UNION ALL
SELECT 'B', 'Y', 'ABC', 821704 FROM dual UNION ALL
SELECT 'B', 'X', 'ABC', 377211 FROM dual UNION ALL
SELECT 'B', 'Z', 'DEF', 945053 FROM dual UNION ALL
SELECT 'B', 'Y', 'DEF', 919120 FROM dual UNION ALL
SELECT 'B', 'Y', 'ABC', 821704 FROM dual UNION ALL
SELECT 'C', 'X', 'ABC', 377211 FROM dual UNION ALL
SELECT 'C', 'Z', 'DEF', 945053 FROM dual UNION ALL
SELECT 'C', 'Y', 'DEF', 919120 FROM dual UNION ALL
SELECT 'D', 'X', 'ABC', 377211 FROM dual UNION ALL
SELECT 'D', 'Z', 'DEF', 945053 FROM dual UNION ALL
SELECT 'D', 'Y', 'GHI', 919120 FROM dual UNION ALL
SELECT 'E', 'X', 'ABC', 377211 FROM dual UNION ALL
SELECT 'E', 'Z', 'DEF', 945053 FROM dual UNION ALL
SELECT 'E', 'Y', 'ABC', 919120 FROM dual UNION ALL
SELECT 'E', 'Z', 'ABC', 945053 FROM dual UNION ALL
SELECT 'E', 'Y', 'DEF', 919120 FROM dual UNION ALL
SELECT 'B', 'X', 'IJK', 326886 FROM dual

CREATE OR REPLACE PROCEDURE "SCHEMA.pivot"(v_recordset out sys_refcursor)
AS
--v_recordset SYS_REFCURSOR;
  v_sql       VARCHAR2(32767);
  v_cols_1    VARCHAR2(32767);
  v_cols_2    VARCHAR2(32767); 

BEGIN
  SELECT LISTAGG( ''''||"level"||''' AS "'||"level"||'"' , ',' )
          WITHIN GROUP ( ORDER BY "level" DESC )
    INTO v_cols_1
    FROM (
          SELECT DISTINCT "level"
            FROM tempt
          );

  SELECT LISTAGG( 'MAX(CASE WHEN category = '''||category||''' THEN "'||"level"||'" END) AS "'||"level"||'_'||category||'"' , ',' )
          WITHIN GROUP ( ORDER BY category, "level" DESC )
    INTO v_cols_2
    FROM (
          SELECT DISTINCT "level", category
            FROM tempt
          );

  v_sql :=
  'SELECT "set", '|| v_cols_2 ||'
     FROM
     (
      SELECT *
        FROM tempt
       PIVOT
       (
        MAX(value) FOR "level" IN ( '|| v_cols_1 ||' )
       )
      )
      GROUP BY "set"
      ORDER BY "set"'; 
  DBMS_OUTPUT.PUT_LINE(v_sql);
  OPEN v_recordset FOR v_sql;
end pivot;

When I execute it I get the following error :- ORA-01489: result of string concatenation is too long ORA-06512 I have seen most stackoverflow answers involving and they all have the same workaround i.e to use xmlagg Sample code the answers have provided is:-rtrim( xmlcast( xmlagg( xmlelement(e, val || ',') order by id) as clob), ',') as clob_agg

I tried incorporating the same in my code and I was unable to get it correctly, if this is the only way to resolve this error , how do I convert my listagg into xmlagg and run it.

Oracle error messages are often misleading, I also want to know if there are any errors in the code front. The proc gets compiled sucessfuly but only during execution it throws the above said error

Ive not able to resolve this yet, its not a front end/ local set up issue Its the error and I dont know how to incorporate the xmlagg in this code