Performing a perform timing facility function instruction for sychronizing TOD clocks

A computer program product for performing a Perform Timing Facility (PTFF) instruction for steering a Time of Day (TOD) clock of a first computer system for synchronizing the TOD clock with TOD clocks of other computer systems, the computer program product comprising:

• a non-transitory storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising:
• obtaining a function code specified in a first general register, said function code for identifying any one of a query function or a control function to be performed;
• obtaining, from a second general register, a memory address of a parameter block;
• responsive to the function code specifying a query function, storing timing information of said computer system in said parameter block according to said specified query function;
• responsive to the function code specifying a control function, using timing information obtained from the parameter block to perform the specified control function;
• and,
• setting a condition code value indicating an outcome of the specified function, a specified control function being a steering rate control function in which said processing circuit performs:
• computing a TOD offset value (d) as a function of a physical clock (Tr), a start time (s), a base offset (b), and a steering rate (r);
• and
• creating a TOD clock by arithmetically adding the TOD offset value (d) to the physical clock (Tr).

A method for performing a Perform Timing Facility (PTFF) instruction for steering a Time of Day (TOD) clock of a first computer system for synchronizing the TOD clock with TOD clocks of other computer systems, said method comprising:

• obtaining a function code specified in a first general register, said function code for identifying any one of a query function or a control function to be performed;
• obtaining, from a second general register, a memory address of a parameter block;
• responsive to the function code specifying a query function, storing timing information of said computer system in said parameter block according to said specified query function;
• responsive to the function code specifying a control function, using timing information obtained from the parameter block to perform the specified control function;
• and
• setting a condition code value indicating an outcome of the specified function, a specified control function being a steering rate control function in which a processor device performs:
• computing a TOD offset value (d) as a function of a physical clock (Tr), a start time (s), a base offset (b), and a steering rate (r);
• and
• creating a TOD clock by arithmetically adding the TOD offset value (d) to the physical clock (Tr), said steering rate value (r) determined by adding a fine steering rate (f) to a gross steering rate (g).