TUNE

Syntax

Where qinfo is written in the following form:

	NOTE: Misuse of this command can significantly degrade system operating efficiency.

OPERATION

The system manager uses the TUNE command to change the characteristics of the circular scheduling subqueues to more efficiently manage the current processing load.

A process in the CS, DS, or ES scheduling subqueues typically begin execution at the base priority. When the process stops (for disk I/O, terminal I/O, preemption, etc.), the amount of CPU it has consumed is used to determine its new priority. If the process has completed a Dispatcher transaction, typically by issuing a terminal read, its priority is reset to the base, and the quantum value for that workgroup is recalculated. If the process has exceeded the quantum (filter) value since its priority was last reduced, the priority is decreased without exceeding the limit priority. If the boost property for the workgroup is oscillate, process priorities are reset to the base value once they decay to the limit.

The parameters min and max refer to the absolute bounds of the quantum, or a filter representing the average transaction time of processes in that subqueue. The quantum is recomputed after every user Dispatcher transaction is complete, and then compared against the CPU time of a process to determine whether the priority of the process should be decreased.

	NOTE: With Release 5.0 of MPE/iX, all three circular scheduling subqueues, CS, DS, and ES, have dynamically calculated quantums. By default, the DS and ES subqueues have their bounds set to the same value.

If the values specified for max are too large, system response may become erratic. If they are too small, excessive memory management may occur due to frequent process swapping. Either case degrades system performance. The values for min and max may range from 1 to 32,767. The recommended settings are listed in the table below.

The timeslice value determines how long a process in a given scheduling subqueue will be allowed to hold the CPU. This value is different than the quantum, which determines how rapidly process priorities decay. The timeslice does interrupt the process if the process is interruptable. The timeslice is a multiple of 100 milliseconds and has a minimum value of 100 milliseconds.

The following default settings are established when the system is booted from the system disk (a START RECOVERY or START NORECOVERY), unless the user has customized a TUNE configuration.

 START RECOVERY or START NORECOVERY
 
 CQ base: 152  DQ base: 202  EQ base: 240
   limit: 200    limit: 238    limit: 253
      min:  1     min: 2000     min: 2000
     max: 2000   max: 2000      max: 2000
  boost: DECAY  boost: DECAY  boost: DECAY
    tslice: 200  tslice: 200     tslice: 200

	NOTE: The MPE/iX Scheduler now supports the workgroup concept. However, backward compatibility is maintained through five default workgroups created by the system. The scheduling characteristics of the CS_Default, DS_Default, and ES_Default workgroups mimic those of the CS, DS, and ES scheduling subqueues. In fact, changing the scheduling characteristics of the CS, DS, and ES scheduling subqueues, via the TUNE command, is equivalent to changing the characteristics of the corresponding default workgroup through ALTWG. Please refer to the NEWWG and ALTWG commands for more detail. Workload Manager users should use ALTWG rather than TUNE since TUNE does not modify user-defined workgroups. If you aren't using Workload Manager, and you want to change one of the system-defined workgroups, you may wish to use ALTWG because it only examines member processes of a specific workgroup and not all processes on the system.

The TUNE command may be issued from a session, job, program or in BREAK. Pressing Break has no effect on this command. TUNE requires System Supervisor (OP) or System Manager (SM) capability.

EXAMPLE

To set the CS subqueue's base to 152, limit to 200, and max quantum (filter) to 300; and the DS subqueue's base to 202, limit to 238, min and max quantum (filter) to 1000, and cause oscillation boosting, enter:

 TUNE CQ=152,200,300,300;DQ=202,238,1000,1000,OSCILLATE

To set the CS subqueue to oscillation with a 300 millisecond timeslice and the DS subqueue's base to 180, limit to 238, boost property to decay, and timeslice to 1500, enter:

 TUNE CQ=,,,,OSCILLATE,300;DQ=180,238,,,DECAY,1500