1. A computer-implemented method for performing backup of a database, the method comprising: maintaining a database system storing a plurality of database objects; receiving, by the database system, a first backup command; executing the first backup command, comprising backing up a first data set of the database; receiving an alter backup command specifying modifications to data sets backed up by subsequent backup commands, the alter command identifying one or more database objects and information indicating whether to include or exclude data of each identified database object from data sets backed up by subsequent backup commands; receiving a subsequent backup command responsive to the alter backup command; and executing the subsequent backup command, comprising, backing up a second data set, wherein the second data set differs from the first data set in accordance with the alter backup command.