Changes the scheduling characteristics of the scheduling
queues. These characteristics include base and limit
priorities, quantum bounds (min and max), boost property
Misuse of this command can significantly degrade system operating efficiency.
minclockcycle THIS PARAMETER IS IGNORED. IT APPEARS HERE FOR MPE
V/E COMPATIBILITY ONLY.
base An integer from 150 to 255 specifying the priority
at which user processes executing in the CS, DS,
and ES scheduling queues begin their Dispatcher
transactions. Priority is inversely related to the
integer: a higher-priority process has a lower
number. While the full range is provided for
compatibility, avoid setting the base priority
between 150 and 152, since user processes running
at priorities greater than 152 can adversely affect
limit An integer specifying the lowest priority at which a
process in the CS, DS, or ES scheduling queues can
execute. Priority is inversely related to the
integer: a higher-priority process has a lower
number. The limit, which can range from 150 to 255,
must be greater than or equal to the base.
min The minimum quantum is a lower bound for the
dynamically calculated quantum (average transaction
time) value. The quantum value determines the
rate of priority decay for processes within the
scheduling queue. Values range between 1 and
max The maximum quantum is an upper bound for the
dynamically calculated quantum (average trans-
action time) value. The quantum value determines
the rate of priority decay for processes within
the scheduling queue. Values range between 1 and
32767 milliseconds. The value of max must be
greater than or equal to the value of min.
DECAY Indicates if the queue is to demonstrate the default
decay behavior associated with circular queues
If set, a process decays normally to the limit of
the queue and returns to the base when the
transaction is completed. DECAY is the default.
OSCILLATE Indicates if the queue is to demonstrate
oscillation. If set, a process is placed back
to the base of the queue once its priority has
decayed to the limit of the queue, even if it has
not completed a dispatcher transaction.
tslice The number of milliseconds a process in a
given queue can keep the CPU once it gets
the CPU. A process holding the CPU for
this number of milliseconds will be
timesliced. This value is accurate to the
nearest 100 milliseconds and has a minimum
value of 100 milliseconds.
The system manager uses the TUNE command to change the
characteristics of the circular scheduling queues
to more efficiently manage the current processing load.
This command may be issued from a session, job, or in BREAK,
but not from a program. Pressing [Break] aborts the
execution of this command. It requires system supervisor (OP)
or System Manager (SM) capability.
Processes in the CS, DS, and ES scheduling subqueues typically
begin execution at the base priority. When a 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
Min and max refer to the absolute bounds of the quantum
("system average quantum", or SAQ) or a filter representing
the average transaction time of processes in the queue.
For the CS, DS, and ES scheduling queues, the quantum is
recomputed after every user Dispatcher transaction is
complete and then compared against the CPU time of the
process to determine whether the priority of the process
should be decreased.
If the values specified for max are too large, system
response may become erratic. If they are too small, excessive
memory management may occur as a result of frequent process
swapping. In either case, system performance is degraded.
The values for min and max may range from 1 to 32,767.
The recommended settings are listed below in the table of
default values for START RECOVER or START NORECOVER.
A user Dispatcher transaction completes under several
circumstances, including the following:
o waiting for a terminal read
o waiting for a parent or child wait
o waiting for an IPC message file
o waiting for the PAUSE intrinsic if pause time exceeds one second
Parameters are positional. For example, to change min
without specifying base and limit, precede it with commas.
The following default settings are established when the system
is coldloaded from the system disk (a START RECOVER or START
NORECOVER). The values assigned for limit specify the lowest
priority (largest number) that the system can assign to a
process in a particular queue.
START RECOVER or START NORECOVER
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
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 queues. In fact, changing the scheduling
characteristics of the CS, DS, or ES queue via the TUNE command is
equivalent to changing the characteristics of the corresponding default
workgroup through ALTWG.
Workload Manager users should use ALTWG rather than TUNE since TUNE
does not modify user-defined workgroups. If you aren't using the
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.
To change more than one system-defined workgroup, TUNE, which allows you
to specify the CQ, DQ and EQ in a single command, is more efficient.
To set CQ base to 152, limit to 200, and CQ maximum filter
to 300; and DQ base to 202, DQ limit to 238, DQ (and EQ)
minimum and maximum filter to 1000, and cause oscillation
To set the CS queue to oscillation with a 300 millisecond
timeslice and the DS queue's base to 180, limit to 238,
boost property to decay, and timeslice to 1500, enter:
Commands: SHOWQ, ALTPROC, SHOWPROC, NEWWG, ALTWG, PURGEWG, SHOWWG
Manuals : Process Management Programmer's Guide (32650-60011)