about use schedule to backup a database on Maxdb76

Hello,everyone.

I want use schedule to backup a database on Maxdb76, occurs these error.

1.dbmcli -d hoteldb -u dbm,dbm 
  dbmcli on hoteldb>util_connect
  dbmcli on hoteldb>backupstart completebak DATA 
  >ok
but when I excute commands as follows:
2.dbmcli -d hoteldb -u dbm,dbm util_connect
  >ok
  dbmcli -d hoteldb -u dbm,dbm backupstart completebak DATA 
  >ERR
  -24992,ERR_NOUTILSESSION: no utility session available
3.dbmcli -d hoteldb -u dbm,dbm scheduler_create_job 10:00:00 util_connect
  dbmcli -d hoteldb -u dbm,dbm scheduler_create_job 0 backupstart completebak 
DATA 

  >ERR  -24992
who can tell me why the error appeared? And how I sattle the second intance and 
the thd.Thanks.