Report history is a collection of previously run copies of a report. You can use report history to maintain a record of a report over time. Report history is an extension of a report. If you move a report, report history moves with it. However, if you modify a report or delete its data source, existing report history is preserved.
Report history is not intended for reports that contain confidential or personal data. For this reason, report history can include only those reports that query a data source using a single set of credentials (either stored credentials or credentials used for unattended report execution) that are available to all users who run a report.
Report history consists of report snapshots: instances of a report that contain layout information and data obtained from an external data source at specific points in time. Each snapshot in report history captures a report as it was when the snapshot was created. If you change the layout or delete the data source, snapshots in report history remain intact.