Every time you access a data item in the cache structure (through a READ_DATA or WRITE_DATA request), the system sets the directory reference bit to indicate that the data item is recently referenced. You can use IXLCACHE RESET_REFBIT to test and reset the directory reference bit settings. Using RESET_REFBIT can help determine how efficiently you are using cache structure storage. If the number of recently referenced data items is low compared to the total number of cached data items, your cache structure might be too big, and you might not be making good use of cache structure resources. If the percentage of recently referenced data items relative to the total number of data items in the cache structure is high, your cache structure might be too small.

For each recently referenced data item that the system scans, the RESET_REFBIT request resets the reference bit to make them appear to be “unreferenced.” (When you issue RESET_REFBIT to reset the reference bit for a data item, the system does not change the order of the data entry on the storage class queue.) After a set interval, you can test again to measure resource usage.