Clipboard data and Datapage data are stored in memory.
For the clipboard, objects are typically opened onto the clipboard from the database, then the clipboard holds the data (and any adjustments) until it is persisted back to the database. For more information, you can check out this article:
Datapages are loaded either from the Pega database, or from external sources, and held in memory at a configurable scope for a configurable time period. More information can be found in the below article:
Some more information about the "Clipborad" and the "Data page" :
"A clipboard is a temporary memory area on the server that is associated with every connected Pega Platform requestor, including browser-based users and unauthenticated guest users. The clipboard has a hierarchical structure, consisting of nodes known as pages, most of which have a name and an associated class. "
"A data page is used to cache data on demand to a clipboard page for use by one or more applications. A data page rule defines the source, scope, refresh strategy, editability, and structure of the cached data. Data pages were previously known as declare pages."