When modifications are made to rows in system-versioned system-time tables, Teradata Database provides automatic handling of the system-time period as needed to maintain the information in a time-aware fashion.
DELETE and UPDATE modifications to system-time tables leave permanent records of the changes in the database. Deleted rows are “closed” in system time by having the end of their system-time period set to the time of the deletion. Modifications to rows close the old row in system time, and automatically create new rows to reflect the new information with system-time periods that begin at the time of the modification.
Closed rows persist in system-time tables until they are explicitly removed and physically deleted from the table. This can only happen if the system versioning is explicitly dropped from the table, whereupon all closed rows are automatically deleted.
The mechanism of new rows being automatically generated by Teradata Database for modifications to temporal tables is described in more detail in Modifying Temporal Tables.