Some scaling operations may be accomplished immediately with no downtime (e.g., using Elastic Performance on Demand, or EPOD), and other scaling operations require just a brief restart and no data redistribution.
For permanent system expansion, Teradata systems are available for read-only operations during which users cannot load or change data but can continue to run queries and reports. When the new resources are ready, there will be a few minutes of scheduled downtime to transition from the former to new resources.