In a store-in cache system, changed and unchanged data items might be handled as follows:

• When writing a new data item that is identical to the copy on permanent storage, code CHANGED=NO. You can also code CROSSINVAL=NO and GETCOLOCK=NO, or omit those keywords and use the system defaults.
• When writing a data item that you have read from permanent storage or the cache structure and updated, or when writing an updated data item back to the cache structure, code CHANGED=YES. The system marks the cached data item as changed and invalidates other users' copies of the data item that are in their local cache buffers. The system considers resources for changed data items as ineligible for reclaim.