In this paper, we propose a toolkit called EDOM facilitating the evaluation and optimization of energy-efficient multicore-based database systems. The two core components in EDOM are a benchmarking toolkit and a multicore manager to improve energy efficiency of database systems running on multicore servers. We start this study by analyzing the energy efficiency of two popular database operations (i.e., cross join and outer join) processed on multicore processors. We describe the criteria and challenges of building an energy efficiency benchmark for databases on multicore servers. We build a benchmarking toolkit, which is comprised a configuration module, a test driver, and a power monitor. We develop a multicore manager to optimize the number of cores, thereby making good tradeoff between performance and energy efficiency in multicore database servers. At the heart of the multicore manager is a memory usage model that estimates memory utilization from queries and database characteristics. An appropriate number of cores is determined using the estimated memory usage to avert unnecessary memory swapping. We make use of the proposed benchmark toolkit to quantitatively evaluate the performance of our novel multicore manager. Our benchmarking tool of EDOM shows that the multicore and CPU utilizations have significant impacts on energy efficiency. More importantly, extensive experimental results show that our multicore manager in EDOM provides a simple yet powerful solution for improving energy efficiency of database applications running on multicore servers.