Permanent Journal

The purpose of a permanent journal is to maintain a sequential history of all changes made to the rows of one or more tables. Permanent journals help protect user data when users commit, uncommit or abort transactions. A permanent journal can capture a snapshot of rows before a change, after a change, or both. You use permanent journaling to protect data. Unlike the automatic journal, the contents of a permanent journal remain until you drop them. When you create a new journal table, you can use several options to control the type of information to be captured. 

You create permanent journals when you create a user or database. To create permanent journals within an existing user or database, use the MODIFY statement. Users activate permanent journaling by including the JOURNAL option in the CREATE or MODIFY statements for users or databases. You must allocate sufficient permanent space to a database or user that will contain permanent journals. If a database or user that contains a permanent journal runs out of space, all table updates that write to that journal abort.

Use the MODIFY USER or MODIFY DATABASE statement to delete a permanent journal. Before you delete the journal, you must use the ALTER TABLE statement to stop the journaling being done to that journal. 

Teradata interview questions FAQs

How teradata makes sure that there are no duplicate rows being inserted when its a SET table?
Teradata redirects the new inserted row as per its Primary Index to the target AMP (Access Module Processor) on the basis of its row hash value, and if it find same row hash value in that AMP then it start comparing the whole row, and find out if duplicate.
When the target table has UPI(Unique Primary Index) then the duplicate row is rejected with an error.
In case of a NUPI(Non-Unique Primary Index) then it is rejected without throwing any error