We uses IDS7.31 and Legato Networker.
I thought this :
onbar -b -w will uses only TAPEDEV, this backup your whole database including logical logs.
onbar -l will uses LTAPEDEV.
If you select ALARMPROGRAM=/usr/informix/etc/no_log.sh, what means no logical log backup than will your db hangs when all you logs are consumed and you will have to make a full backup or launch "onbar -l". Else you still hangs.
If you select ALARMPROGRAM=/usr/informix/etc/log_full.sh, what means that the logical logs will be backup then onbar -l will be launched.
With LTAPEDEV /dev/null the logical logs will be send to /dev/null only with "onbar -l".
I made an IDS instance for such experiments.
LTAPEDEV you can change while IDS is running.