已经建好的job，如何让它手工运行？

job号 22linux下面登录数据库，SQL>begin
    dbms_job(22);
    end;
    /
ERROR at line 1:
ORA-23421: job number 21 is not a job in the job queue
ORA-06512: at "SYS.DBMS_SYS_ERROR", line 86
ORA-06512: at "SYS.DBMS_IJOB", line 529
ORA-06512: at "SYS.DBMS_JOB", line 258
ORA-06512: at line 2