Run statspack snapshot every 30 minutes

For example : Run statspack snapshot every 30 minutes

SQL>

SQL>

DECLARE
    jobno number;
    instno number;
BEGIN
    SELECT instance_number INTO instno FROM v$instance;
    DBMS_JOB.SUBMIT(jobno, 'statspack.snap(i_snap_level => 7);',
    trunc(sysdate,'HH24')+((floor(to_number(to_char(sysdate,'MI'))/30)+1)*30)/(24*60),
    'trunc(sysdate,''HH24'')+((floor(to_number(to_char(sysdate,''MI''))/30)+1)*30)/(24*60)', TRUE, instno);
    COMMIT;
END;
/