Which version of DFM are you running?

For 2.x you can try:

Go to DFM->Configuration->Polling and Thresholds ->Managing Thresholds

Here choose on the DFM System Defined Groups->Interface Groups->Dial-On-Demand and

click on Edit

On the new screen that comes up, choose Customize Settings.

Remove Dial-On-Demand Support Settings and add Generic Interface/Port performance settings

and Interface/port flapping settings.

Click on Save.

Go to DFM->Configuration->Polling and Thresholds->Managing Thresholds and choose Apply Changes.

For 1.X:

Go to DFM > Administration Console > Edit > Polling and Thresholds.

Click on the Thresholds tab on the lower left corner of the window.

Expand the groupings until you see the interface that is generating the alarm. (More likely, its under Interface Groups > Backup)

Once you found the group, click on Settings. Highlight Backup Interface Support,

on the right panel, you should see the MaximumUptime setting, move the slider to 0 (zero)

to disable the settings.

Click on Group > Reconfigure, then domain Recompute Codebook.