You can consider the backlog in the capacity availability check, that is, the capacity requirements that lie in the past. The backlog is made up of all capacity requirements between the start of the time period where the database is read and today's date.

You set the start of the time period for reading the database in Customizing (Time profile in the overall profile).

If you want to consider the backlog during the capacity availability check, you must do the following:

During the capacity availability check, the system loads the current and the subsequent periods with the capacity requirements from the past, up to the maximum load limit for the capacities. The available capacity in these periods is therefore reduced by the backlog. The system considers the reduced available capacity during the check and also during finite scheduling in the capacity availability check.