"To have everything is to possess nothing.“
INSERT, UPDATE, and DELETE statements change data. Netezza will automatically commit the changes (write to disk) if the request changes all of the rows satisfied by the client. If any failure does occur, then Netezza does a rollback of all the changes automatically.
Situations arise that require multiple changes to multiple tables must be completed successfully to finish the transaction. An automatic commit won't work here because all commands must now work or all commands must fail together.
The BEGIN starts a transaction that will continue until either the keyword COMMIT or ROLLBACK commands are encountered. Any transaction failure or ROLLBACK ...