Combinabilty mode means datastage will combine the operators in a single process.If combinability mode is disabled,the number of Unix processes will increase. It can be set by setting "APT_DISABLE_COMBINATION".(Env variable) Combined operators generally improve performance at least slightly (in some cases the difference is dramatic). There may also be situations where combining operators actually hurts performance, however. Identifying such operators can be difficult without trial and error. The most common situation arises when multiple operators are performing disk I/O (for example, the various file stages and sort). In these sorts of situations, turning off combination for those specific stages may result in a performance increase if the flow is I/O bound. Combinable operators often provide a dramatic performance increase when a large number of variable length fields are used in a flow.