Saveen Reddy discusses parallelism with U-SQL jobs:
Previously an Data Lake Analytics account was limited to a total of 60 units on parallelism available to 3 concurrent U-SQL jobs. And each U-SQL job was limited to only using a maximum of 20 units of parallelism. However, sometimes developers want to run a U-SQL job that uses more parallelism. For example: they might want two concurrently running jobs that each use 30 units. Today, we are removing the per-job limit. Now you can concurrently run jobs that use any amount of parallelism as long as the total for the running jobs doesn’t go beyond the maximum for your account (currently 60 units of parallelism).
If you are already running U-SQL jobs, there’s no need to worry. This change doesn’t require any action on your part. Your jobs run just as they did before. But now, if you want to you can take advantage of all the parallelism in your account.
This doesn’t change the available performance units, so there’s no billing change.