Note that if you use item descriptor inheritance (as described in the Item Descriptor Inheritance section of this chapter), the parent item descriptor and all of its children use the same item cache. As a result, all item cache configuration (including cache mode and item cache size) for all the item descriptors in the family should be set in the parent item descriptor, and not in any of the child item descriptors. Note though that the query caches are independent, so you may still set a different query cache size for each of the descriptors in the family.
