Managing unmodified tracks maintained in both a first cache and a second cache

A computer program product for managing data in a cache system and a storage device, the computer program product comprising a non-transitory computer readable storage medium having computer readable program code embodied therein that executes to perform operations, the operations comprising:

• maintaining in a first cache unmodified tracks in the storage subject to Input/Output (I/O) requests;
• demoting unmodified tracks from the first cache to a second cache;
• maintaining an inclusive list indicating unmodified tracks maintained in both the first cache and the second cache;
• maintaining an exclusive list indicating unmodified tracks maintained in the second cache but not the first cache;
• and
• using the inclusive list and the exclusive list to determine whether to promote to the second cache an unmodified track demoted from the first cache.