The parameterization method used by the CLASS statement can have a noticeable effect on the time required by the modeling procedure. The CLASS statement creates numeric design variables that represent the effect of the variables specified in that statement. Some procedures, such as LOGISTIC, GENMOD, PHREG and others offer several parameterization methods via options in the CLASS statement. The most efficient parameterization is the GLM parameterization requested by the PARAM=GLM option in the CLASS statement. This is a less than full-rank parameterization. Full-rank parameterizations, such as PARAM=REF are PARAM=EFFECT, are less efficient. In models with many parameters, the increase in time required with a full-rank parameterization can be considerable. To reduce execution time, use GLM parameterization.