1. A computer program product for handling a hierarchical cache structure, the computer program product comprising: a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: initiating requests to a third level cache of the hierarchical cache structure by an instruction cache and a data cache of a split second level cache of the hierarchical cache structure, the hierarchical cache structure comprising at least one higher level cache with a unified cache array for data and instructions and at least two lower level caches, each split in an instruction cache and a data cache; and initiating requests by an instruction cache of a split first level cache to said instruction cache of said split second level cache, and initiating requests by a data cache of said split first level cache to said instruction cache and said data cache of said split second level cache.