The group, or groups, over which the function operates, depending on the evaluation of the specified condition. If the condition evaluates to TRUE, a new dynamic partition is created inside the specified window partition.
RESET WHEN is optional. If there are no RESET WHEN or PARTITION BY clauses, then the entire result set constitutes a single partition.
If there is no PARTITION BY or RESET WHEN clauses, then the entire result set, delivered by the FROM clause, constitutes a partition.