What is Clipboard in PEGA PRPC

Clipboard is nothing but a tempary memory area.it contains a some pages.The clipboard has a hierarchical structure, consisting of sub areas known as pages, which may have a name.Most pages have an associated class, and act as buffers or temporary copies of object instances (of that class) that are copied from, or may later be stored into, the rulebase or a database.

Clipboard (Contents) 

The contents of a page is an unordered list of unique property names and optionally a value for each property.

Properties are added to the clipboard by activities as they execute, and by user input received through <FORM > inputs and Submit buttons.

Some clipboard pages may contain other pages, either as embedded pages or as the value of a property which has a property mode of Page, PageList or PageGroup. These pages may in turn contain other pages.

Clipboard (Categories of Pages)

The clipboard contains four broad categories of top-level pages:

User pages
The requestor page
The result page
The thread page 

Differences between Clipboard Viewer, Clipboard and Database

The Clipboard Viewer shows a subset of the data in the clipboard.

The Clipboard, stored in the memory of the server, is a temporary structure associated with each requestor.It consists of an unlimited number of pages that contain temporary property-value pairs.Activities move data from the clipboard to and from the database.It cannot be viewed directly.

The database is a permanent structure stored on the database server. Adding a property to the clipboard is the first step to saving it to a database. The only way to save a property to a database is to first put the property on a clipboard page, and then to use the Obj-Save, Commit, or RDB-Save method in an activity to send the page containing the property to the database.