With the batch file , we can run sessions either in sequential or in concurrently. Grouping of Sessions is known as Batch. Two types of batches :
1)Sequential: Runs Sessions one after another. 2)Concurrent: Run the Sessions at the same time.
If you have sessions with source-target dependencies you have to go for sequential batch to start the sessions one after another. If you have several independent sessions you can use concurrent batches Which run all the sessions at the same time.