When tags are stored in the Canary Historian, they are organized into DataSets. A DataSet is simply a user-defined organizational subset or grouping of tags. An administrator can create as many DataSets within the Canary Historian as necessary. To learn more about how to create DataSets, read this article: How to Create and Configure a Dataset?
DataSets play a key role in logging, storing, and reading data.
During the logging process, you must identify which DataSet within the Canary Historian each tag will be stored within. Each logging configuration file (LCF file) should only target a single DataSet. This best practice is recommended so that if a logging session is stopped, it will only interrupt a single DataSet.
As tag values are written, each DataSet records those values in its own Historical Database file (HDB file). By default, a new HDB file is created per DataSet daily. To learn more about HDB files and how to configure them, read this article: How does Canary store Historical Database Files