I would recommend manually coding your categorical variables if you want to use effect coding. For example, if you have a categorical variable called hospital with values of "Hospital A", "Hospital B", and "Hospital C", rather than entering hospital into proc glimmix in the class statement, instead create two new variables, "Hospital_A" and "Hospital_B" (Hospital C is arbitrarily designated the reference group). If hospital = "Hospital A", then Hospital_A = 1, hospital = "Hospital B", then Hospital_A = 0, and if hospital = "Hospital C", then Hospital_A = -1. Use the same logic for the Hospital_B variable. Manual coding allows you to choose which category to use as a reference and directly find the effect code coefficients in the Solutions for Fixed Effects output (use the "solution" option in the model statement). I would also use manual coding when using weighted effect coding, when there are an unequal number of observations across categories.
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