A Drop Rule is a validation rule. Drop is shorthand for Drop From Process.
Drop Rules work in close conjunction with payload state. When a drop rule executes two optional events are available:
1. The data payload in question is pended in K3. It is not sent further downstream.
-Persistence set to: True -The data payload caught by the when statement is saved.
-Persistence set to: False -The data payload caught by the when statement is purged.
2. An email alert is generated.
Alert set to: True -An email alert is generated about the data payload
Alert Set to: False - No alert is generated
For example, some data sources occasionally incorrectly populate fields. Let's say that an upstream system send a field to K3 with no data. This will cause problems for the Target system. Thus, we can set up a Drop Rule to ensure that empty data is brought to our attention for correction.
When important_field = null
Then Drop Persistence = True Alert = True
This will hold the dropped payload until is manually re-pushed downstream. See this article.