The CDHDR and CDPOS table contains information related to changes of a specific entity. Using these tables you can track how many times the value of an entity has changed and especially to which value. Because the CDHDR and CDPOS tables contains alot of data it is advisable to restrict the table during data extraction.
Using a restriction on OBJECTCLASS you have the ability to only select those records related to a specific SAP entity for e.g. Sales Orders (VERKBELEG), Purchase Orders (EINKBELEG) or Handling Units (HANDL_UNIT). To determine which filter must be setup the table TCDOBT can be used. This table stores all object classes available in the system.