1 of 1 people found this helpful
This is a default behavior for bulk data calls which can be changed in the AF Configuration database. Here is a note from PI Web API - Cache-Control headers documentation:
Due to performance considerations, you cannot use the Cache-Control header on bulk data operations by default. However, you can change this setting by adding/setting a Runtime configuration IgnoreCacheControlForBulkRequests item and setting Value Type to Boolean and Value to true. See Configuration at runtime .