In multi-context Dynamically Reconfigurable Processor Array (DRPA), the required number of contexts is often increased by those with low resource usage. In order to execute such contexts without wasting a context memory, we propose anew execution mode called instruction buffer mode in addition to the normal multi-context mode. In this mode, a configuration code from the central configuration memory is stored in the instruction buffer and executed directly. Furthermore, by exploiting a multicast method, a single configuration code loaded to the buffer can be executed by multiple processing elements in a SIMD fashion. We also investigate a mode selection policy based on simple formulas. From the result of implementation and evaluation by using a prototype DRPA called MuCCRA-1, it appears that the total execution time is reduced 12% by using the instruction buffer mode, while 12% of the semiconductor area is increased.