Which of the following statements is true about rollup fields?

Rollup fields are designed to aggregate data from related records and provide a summary calculation. One of their key characteristics is that they operate asynchronously and are calculated on a scheduled basis. This means that the rollup field does not update immediately when data changes, but rather on a pre-defined schedule set by the system, which usually runs every hour. This allows for efficient processing and management of data without impacting system performance by requiring immediate calculations upon data changes.

The ability to schedule rollups is important as it ensures that the system remains responsive and can handle batch processing of calculations at set intervals. Meanwhile, the other options do not accurately represent how rollup fields function. Since rollups do operate on a schedule, asserting that they calculate as soon as a new record is added or immediately upon system restarts misrepresents their asynchronous nature. Additionally, the claim that the schedule cannot be adjusted is misleading; while there are limitations on the frequency of rollups, the default schedule can indeed be set to certain intervals as defined in the system settings.