Data pages on the clipboard Data pages on the clipboardA data page is a clipboard page created by execution of a data page (Rule-Declare-Pages rule type).
The name of a data page starts with the prefix D_ or Declare_. Such pages are created and updated only through operations identified in a data page rule. The contents of these pages are visible but read-only to requestors.
Data pages can improve performance and reduce memory requirements when all or many requestors in an application need to access information.
For example, a data page may hold last night's closing U.S. stock prices in a Value Group property indexed by ticker symbol, so that the property reference D_Stock.Price("IBM") is the closing price for IBM shares. The first time each evening (after the 4:30 P.M. New York market close) that a requestor attempts to access the page, the system automatically loads the page with the latest end-of-day prices. The page can remain unmodified in memory until the next day's closing.
Even more significantly, you can reference data pages using parameters, and the data page can create on the clipboard unique instances of itself for each unique reference, with data related to the parameter values. For instance, a single data page, D_Customer, can create many instances of itself on the clipboard as your application requires, and each instance has exactly and only the information about that particular customer.
In other situations, data values are not static but may change infrequently; the system automatically checks the data page contents (using a when condition rule) before each property access to see whether a fresh recomputation is needed. For example, a page may list the part numbers or SKU numbers of items that are out-of-stock, extracted from an inventory control system. Recomputation is needed only as often as an out-of-stock condition begins or ends, not each time the inventory changes.
Data pages are not created at system startup; they are created only when first accessed.
Ordinarily, data pages do not persist; they are not saved to the PegaRULES database but are reconstructed when next accessed and the previous version is expired.
On the Clipboard tool display, data pages appear as a group named Data Pages.
On the Performance tool full details display, you can review (for your own requestor session) elapsed time and CPU time statistics associated with creating, finding, and accessing data pages, and counts of the number of node-level data pages your requestor has accessed.
The system maintains node-level data pages in a cache.
|
expired page, node, page |
|
About Data Pages
Understanding page names and reserved pages Understanding caching About the Performance tool |
|
Atlas — Standard Data Pages rules |
Definitions