Dear all Informix gurus

I am quite new for informix database while now I'm responsible to administration of Informix database. And now I have a problem with Informix On-BAR backup.
In 'onconfig' file, the current configuration is as below

TAPEDEV /dev/rmt0
LTAPEDEV /dev/null

When I fire command 'onbar -b -L0', the output is nice and no problem generated in bar_act.log file. But when I need to backup logical log file with command 'onbar -l', the output is as below

Log backup to device '/dev/null' not allowed

What should I do? Do I need to change LTAPEDEV value from /dev/null to /dev/rmt0 (which is tape device).

Thank you for advanced

Modify LTAPEDEV from /dev/null to non /dev/null

TAPEDEV if for db backup
LTAPEDEV is for logical logs backup
you can change LTAPEDEV without bouncing the informix server