Most scheduling problems including DAG(Directed Acyclic Graph)-based are known to be NP-complete, so many heuristic-based scheduling algorithms have been researched. HEFT and CPOP are such algorithms which have been devised to be effective in heterogeneous environment. We proposed, in the previous research, three scheduling algorithms which are effective in realistic global heterogeneous environment: CPOC, eCPOPC and eCPOP. In this paper, the heuristics which are used in the above five algorithms will be systematically analyzed. Those algorithms will be also studied experimentally using various benchmarks. Experimental results show that the eCPOC generates better schedules than any other algorithms and the heuristics which are used in the proposed algorithms are effective in the global heterogeneous environment.