A method, program product, and system for a transaction parallelization improvement metric calculation includes receiving tracking data. The tracking data includes information about inbound and outbound subtransactions between domains over a time frame. Each domain includes at least one computer. Using the tracking data received, a number of interactions are determined based on a number of the inbound and outbound subtransactions. A total number of domains is determined using received tracking data. A transaction parallelization metric is calculated using the tracking data and a transaction parallelization improvement metric is calculated based on the number of interactions, the number domains, and the transaction parallelization metric.