How can I compute omega and eta squared in SAS after proc glm? | SAS FAQ

After you perform an ANOVA using proc glm, it
is useful to be able to report omega or eta squared as a measure of the strength of the
effect of the independent variable.  Proc glm does have an “effectsize” option
that computes this. Here is an example that shows how to compute
ω²  and η², as well as partial and semi-partial versions.

proc glm data = in.hsb2;
  class race ses;
  model write = race ses/ss3 effectsize;
run;
quit;