For example, suppose that you create a media set named Weekly with an overwrite protection period of seven days, and an append period of 0 days, and you schedule a full backup job to run each Friday at 20:00. When it is time for the full backup to run at 20:00 the following Friday, the job cannot run because the first backup job that ran the previous Friday did not complete until 21:10 p.m. The overwrite protection period for the Weekly media set still has 70 minutes remaining.
Typically, to prevent this situation, you would shorten the overwrite protection period to account for the amount of time a job may run. For this example, the scheduled job recurring at 20:00 can run if the overwrite protection period is set to 6 days instead of 7 days.