SQL & PL/SQL

I have a compound trigger which three DML statements in it. And one of my job is failing because of this trigger with the error "ORA-12838: Object cannot be read/changed after parallel change error". Since commit cant be done in a trigger, what will be the best option to fix this issue. The error occurs after the insert statement.

CREATE OR REPLACE TRIGGER dup_ct
FOR INSERT ON test1
COMPOUND TRIGGER

    TYPE a_records IS TABLE OF test1%ROWTYPE
                 INDEX BY PLS_INTEGER;
    
    new_records a_records := a_records ();
    rows_inserted   PLS_INTEGER := 0;
    v_dup       PLS_INTEGER;

  BEFORE EACH ROW IS
  BEGIN
    rows_inserted := rows_inserted + 1;
    new_records (rows_inserted).class_id  := :NEW.class_id;
    new_records (rows_inserted).mark      := :NEW.mark;
    new_records (rows_inserted).std       := :NEW.std;
    new_records (rows_inserted).res_date  := :NEW.res_date;
    new_records (rows_inserted).exam_date := :NEW.exam_date;
  END BEFORE EACH ROW;

  AFTER STATEMENT IS
  BEGIN
    FOR j IN 1 .. rows_inserted
    LOOP
      SELECT COUNT (*)
      INTO   v_dup
          FROM   test1
      WHERE  mark      = new_records (j).mark
          AND    std       = new_records (j).std
          AND    res_date  = new_records (j).res_Date
      AND    exam_date = new_records (j).exam_date;

      IF v_dup > 1
          THEN
        INSERT INTO test2 (     class_id,                mark,                 std
                     ,      res_date,            exam_date)
            VALUES ( new_records(j).class_id, new_records (j).mark, new_records (j).std
                   , new_records(j).res_date, new_records (j).exam_date);

     delete from test1 select * from test2;
    END IF;
     END LOOP;
  new_records.DELETE;
  rows_inserted := 0;
  END AFTER STATEMENT;
END dup_ct;
/