Which legacy tool is used for high-performance updates in Teradata?

Multiload is the legacy tool designed specifically for performing high-performance updates in Teradata. It allows for the efficient loading of large volumes of data into Teradata tables while also providing the ability to update existing data. This capability is particularly valuable in scenarios where you need to modify or insert data in bulk effectively, making Multiload a go-to choice for ETL (Extract, Transform, Load) operations.

In contrast, the other tools mentioned serve different functions. Fastload is primarily used for loading data into empty tables and is optimized for initial data loads rather than updates. Teradata Unity focuses on workload management and system performance but does not specifically cater to data updates. Teradata Studio is an integrated development environment for database management and does not specialize in high-performance data operations. Thus, Multiload stands out as the correct choice for high-performance updates in Teradata.