A workload scheduler supporting the definition of a cumulative weighting index is proposed. The scheduler maintains (384-386) a profile for each job; the profile (built using statistics of previous executions of the job) defines an estimated usage of different resources of the system by the job. A tuning module imports (304) the attributes of the jobs from the profile. The attributes of each job are rated (306-307) according to an estimated duration of the job. The rated attributes so obtained are then combined (308-320), in order to define a single cumulative index for each job and a single cumulative index for each application (for example, weighting the rated attributes according to corresponding correction factors). In this way, the cumulative indexes allow an immediate comparison (324-356) of the impact of the different jobs/applications of a plan on the whole performance of the system.