I am not seeing any information on this so I thought I'd ask the smart minds here ;-). Are Teradata backups consistent as at the backup start time or end time?
At the start of the backup.
Normally, Teradata places a read lock on the table while it's doing a backup, so the data in a table can't be updated until the lock is released.
If you use the "online backup" feature, Teradata will initially place a brief read lock on the table(s) to get a consistent point (quiesce point) and then it will release this and allow updates to take place on the table(s). During the backup process, Teradata keeps a log of the updates that took place during the backup process. It then takes another read lock at the end of the backup process to get to another consistent point. When you restore from an "online backup", Teradata will restore the data blocks as they were backed up, and then will un-do the updates that took place while the backup was being done, thus restoring the table(s) to the quiesce point at the start of the backup.
If you use permanent journaling on your tables, there are also other options for returning tables to "points in time", without the need to do a backup for each of these points in time by creating "quiesce points" that can involve also multiple tables.