Oracle 21c

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
CREATE OR REPLACE PROCEDURE my_process 
IS
  myjson   VARCHAR2 (32767):= '{"responseinfo":"<TRANSACTION><RESPONSE_CODE>100</RESPONSE_CODE><RESPONSE_MSG>Duplicate Request Found.</RESPONSE_MSG></TRANSACTION>"}';
  l_json_obj    JSON_OBJECT_T;
  requestinfo   VARCHAR2 (32767);
BEGIN
  l_json_obj := JSON_OBJECT_T.parse (myjson);
  requestinfo := l_json_obj.get_string ('requestinfo');
  DBMS_OUTPUT.PUT_LINE(requestinfo);
END;
/
BEGIN
  DBMS_OUTPUT.ENABLE;
  my_process;
END;
/
1 rows affected

dbms_output:


CREATE OR REPLACE PROCEDURE my_process 
IS
  myjson   VARCHAR2 (32767):= '{"responseinfo":"<TRANSACTION><RESPONSE_CODE>100</RESPONSE_CODE><RESPONSE_MSG>Duplicate Request Found.</RESPONSE_MSG></TRANSACTION>"}';
  l_json_obj    JSON_OBJECT_T;
  requestinfo   VARCHAR2 (32767);
BEGIN
  l_json_obj := JSON_OBJECT_T.parse (myjson);
  requestinfo := l_json_obj.get_string ('responseinfo');
  DBMS_OUTPUT.PUT_LINE(requestinfo);
END;
/
BEGIN
  DBMS_OUTPUT.ENABLE;
  my_process;
END;
/
1 rows affected

dbms_output:
<TRANSACTION><RESPONSE_CODE>100</RESPONSE_CODE><RESPONSE_MSG>Duplicate Request Found.</RESPONSE_MSG></TRANSACTION>