HWN021516E The LSS specified LSS name on subsystem Name of subsystem is already at the maximum volume number (255). Volume creation can not be done on this LSS, please select a different one.
Explanation
Only 255 volumes can be created on a particular LSS. IBM Spectrum Control believes that this LSS is full because the highest numbered volume on the LSS is 255.
Action
If volume number 255 has been deleted, try rerunning a probe of the subsystem. Otherwise, either choose a different LSS or else delete volume #255 (and any others as necessary depending on the number of new volumes needed)