Data in AmpUsage points to what time interval?? Is it the current data only? or gets accumulated for some time?
And as mentioned in the documentation, we have to purge it manually i.e. through queries. Does this mean that it is accumulated since Teradata database started? If yes, then how can we know the time interval of the data present in AmpUsage view.
AmpUsage is cumulative by user and account name. For finer granularity, just vary the account name over time. You can use the "account string expansion" feature to have this done automatically for you. See chapter 3 in the Performance Management manual for details.