Oracle JSON ADT in Collection
$ oerr ora 40573
40573, 00000, "Invalid use of PL/SQL JSON object type."
// *Cause:  An attempt was made to use a PL/SQL JavaScript Object Notation
//          (JSON) object type in an invalid context.
// *Action: Use PL/SQL JSON object types only inside PL/SQL.


Example:

set serveroutput on
declare
  l_objects tmp_011040_t2;
  l_index pls_integer;
begin
  l_objects := tmp_011040_t2();
  l_objects.extend(1);
  l_objects(l_objects.last) := JSON_OBJECT_T.parse('{"a":"1","b":"1"}');
  l_objects.extend(1);
  l_objects(l_objects.last) := JSON_OBJECT_T.parse('{"a":"2","b":"2"}');
  l_index := l_objects.first;
  while (l_index is not null)
  loop
    dbms_output.put_line(l_objects(l_index).get_string('a'));
    l_index := l_objects.next(l_index);
  end loop;
end;
/

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PL/SQL procedure successfully completed.