SVC 109 provides you with extended SVCs that are available for you to define. Extended SVCs with function codes 0-199 are reserved for IBM®. You may define only extended SVC with function codes 200-255. SVC 109 assumes the characteristics of a type 3 or 4 SVC. You can use the SVCUPDTE macro to specify those attributes your extended SVC routine requires, such as: locks required, restriction to APF authorized callers only, non-preemptable, and whether the SVC can be called from AR mode. Place the extended SVC routine in the LPA list and name the routine IGX00yyy where yyy is the number (200 - 255), in character format, that is loaded into register 15.