A method, apparatus, system, and signal-bearing medium that, in an embodiment, divide transactions performed by a program into groups, save data regarding duration times of the transactions in response to trace statements in the program, and determine a reliability of the groups of transactions based on the duration times and a number of failures of the transactions in the groups. The duration times are based on differences between start times and end times of the transactions, excluding differences between the suspend times and resume times of the transactions.