Use System Setting rules (Rule-Admin-System-Settings rule type), not Dynamic System Settings (Data-Admin-System-Settings) to hold important constant values in your application that are the same in every deployed copy of your application. Use Dynamic System Settings when the values may differ from site to site — such as URLs, user names, or port numbers — and may be set programmatically.
Your application can create, set, or query instances of this class using Java methods in the PublicAPI PRSystemSettings interface:
The standard DataPages rule Declare_CachedDataSystemSettings creates a Node-scope declare page, refreshed every 10 minutes, containing your system settings. Fetching a value from this in-memory page — by referencing a property — is faster than using the PublicAPI functions listed above, as no database accesses are required. If your application includes dynamic system settings that are frequently accessed, you can override the default load activity LoadDataSystemSettings for this Data Page rule to include them on the data page rule. In your activity, use the function rule @getDataSystemSetting() to look up the value.
Some Dynamic System Settings instances are created automatically during installation or upgrade of a Pega 7 Platform system.