If you have enabled dump and load to the same group, without replace mode enabled:
If a valid plan exists for the query, it is loaded and used to optimize the query.
If a plan exists that is not valid (say, because an index has been dropped) a new plan is generated and used to optimize the query, but is not saved.
If the plan is a partial plan, a full plan is generated, but the existing partial plan is not replaced
If a plan does not exist for the query, a plan is generated and saved.
With replace mode also enabled:
If a valid plan exists for the query, it is loaded and used to optimize the query.
If the plan is not valid, a new plan is generated and used to optimize the query, and the old plan is replaced.
If the plan is a partial plan, a complete plan is generated and used, and the existing partial plan is replaced. The specifications in the partial plan are used as input to the optimizer.
If a plan does not exist for the query, a plan is generated and saved.