Solaris tuning variables come in a variety of forms. The tune structure defined in /usr/include/sys/tuneable.h is the runtime representation of tune_t_gpgslo, tune_t_fsflushr, tune_t_minarmem, and tune_t_minasmem. After the kernel is initialized, all references to values of these variables are found in the appropriate field of the tune structure.
Various documents (for example, previous versions of Solaris System Administration Guide, Volume 2) have stated that the proper way to set variables in the tune structure is to use the syntax, tune:field-name where field name is replaced by the actual variable name listed above. This process silently fails. The proper way to set variables for this structure at boot time is to initialize the special variable corresponding to the desired field name. The system initialization process then loads these values into the tune structure.
A second structure into which various tuning parameters are placed is the var structure named v. You can find the definition of a var struct in /usr/include/sys/var.h. The runtime representation of variables such as autoup and bufhwm is stored here.
Do not change either the tune or v structure on a running system. Changing any of the fields of these structures on a running system might cause the system to panic.