The present disclosure relates to storing data in a computer system. The computer system comprising a main memory coupled to a processor and a cache hierarchy. The main memory comprises a predefined bit pattern replacing existing data of the main memory. Aspects include storing the predefined bit pattern into a reference storage of the computer system. At least one bit in a cache directory entry of a first cache line of the cache hierarchy can be set. Upon receiving a request to read the content of the first cache line, the request can be redirected to the predefined bit pattern in the reference storage based on the value of the set bit of the first cache line.