How is data redistributed when I add new hardware to an existing Teradata configuration?

A reconfiguration utility is provided with the DBMS to enable you to add new hardware with minimal intervention and system unavailability. Hash buckets are assigned evenly across all parallel units (AMPs) within the Teradata system and are used by the file system to target data row placement so a table's data is evenly distributed across all AMPs. When new nodes (and with them new AMPs) are added, a subset of these hash buckets is reassigned in order to include the new nodes in the even spread of data. Data rows associated with the reassigned hash buckets are migrated onto the new AMPs on the new nodes.

This utility only moves the proportion of data equivalent to the percentage of increase in number of AMPs, while leaving the majority of the rows untouched. All tables and indexes are automatically relocated over the internal high speed interconnect, in parallel on all nodes simultaneously, by issuing just a single command. When the reconfigure is complete, the entire system, including all tables and indexes, is immediately and fully available, without the need to rewrite load scripts or make any changes to jobs, queries or database parameters.