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ALTWG
Alters the scheduling characteristics of an existing workgroup. (Native
Mode)
SYNTAX
ALTWG [WORKGROUP=] workgrp [[;BASE=] base] [[;LIMIT=] limit]
[[;MINQUANT=] min] [[;MAXQUANT=] max] [[;BOOST=] {DECAY}]
{OSCILLATE} [[;TIMESLICE=] tslice] [[;MINCPUPCT=] minpercent]
[[;MAXCPUPCT=] maxpercent]
NOTE To alter the membership criteria of a workgroup, you must use the
NEWWG command.
PARAMETERS
NOTE ALTWG follows the CI convention that positional parameters are
allowed until the first high-level keyword is specified.
workgrp The name of the workgroup whose scheduling characteristics
you are modifying. This is a required parameter. Use of
wildcards is not allowed.
base
An integer from 150 to 255 specifying the highest priority
at which processes executing in the workgroup 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 compatability, avoid
setting the base priority between 150 and 152, since user
processes running at a higher priority than 152 can
adversely affect system performance.
limit
An integer specifying the lowest priority which processes
executing in the workgroup can attain. 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 number of milliseconds that a process may use
the CPU before its priority is reduced. The min is a lower
bound for the quantum value, which determines the rate of
priority decay for processes within the workgroup. Values
range between 1 and 32,767, inclusive.
max The maximum number of milliseconds that a process may use
the CPU before its priority is reduced. The max is an
upper bound for the quantum value, which determines the
rate of priority decay for processes within the workgroup.
The value of max must be greater than or equal to the value
of min. Values range between 1 and 32,767, inclusive.
DECAY Sets the workgroup to the default decay behavior associated
with circular scheduling subqueues. If set, a process
decays normally to the limit priority and returns to the
base priority when the Dispatcher transaction is complete.
DECAY is the default boost property.
OSCILLATE Sets the workgroup to oscillate behavior. If set, a
process returns to the base priority once its priority has
decayed to the limit of the workgroup, even if it has not
completed a Dispatcher transaction.
tslice The timeslice is the maximum number of milliseconds a
process in the workgroup can hold the CPU before returning
to the Scheduler to have its priority recalculated. Values
must be multiples of 100, with a minimum value of 100 and a
maximum value of 32700.
minpercent The minimum percentage of time that the CPU is available to
the workgroup's member processes. Within the target
workgroup, this CPU time is allocated according to the
processes' priorities. The workgroup is guaranteed this
minimum percentage even if higher-priority processes in
other workgroups are ready to run.
If the processes in the workgroup do not require as much
CPU time as their guaranteed minimum, that time will be
available to processes in other workgroups. The default
value for this optional workgroup characteristic is that
the workgroup is not guaranteed any minimum CPU allocation
and that CPU allocation is based on process priority only.
maxpercent The maximum percentage of time that the CPU is available to
the workgroup's member processes. The workgroup will be
limited to this maximum percentage of time even if no other
process in another workgroup is ready to run. In other
words, a workgroup will be limited to this maximum
percentage even if the system must remain idle for the
remainder of the time.
The default value for this optional workgroup
characteristic is that there is no maximum which would
prevent a workgroup's processes from getting the CPU time
their priorities warrant.
OPERATION
Each workgroup consists of three components, a name, membership criteria,
and scheduling characteristics. The membership criteria (MEMB_LOGON,
MEMB_PROGRAM and MEMB_QUEUE parameters), determine process assignment,
which occurs on six occasions:
* at process creation
* whenever you change one of the process attributes on which
membership can be based
* when you explicitly move a process to a workgroup via the ALTPROC
command
* when you purge a workgroup, and the subsequent purgescan
redistributes processes to remaining workgroups
* when you add a new workgroup to the current workgroup
configuration
* when the current workgroup configuration is replaced
Membership conflicts are resolved by assigning a process to the first
workgroup for which it qualifies. (Workgroups are maintained in an
ordered list in which position is important. For more information, read
the discussion of the POSITION parameter of the NEWWG command, later in
this chapter.) Since the Workload Manager uses a first-fit algorithm,
other workgroups are not considered once a match is found. For this
reason, it is important to arrange the workgroups in your configuration
from those with the most precise membership criteria to those with more
general membership criteria.
The scheduling characteristics define the scheduling policies which
govern processes within the workgroup. The MPE/iX Dispatcher is
priority-driven, allocating a CPU to the highest priority process that is
ready to run. The MPE/iX Scheduler determines process priorities in
accordance with workgroup scheduling characteristics. Each workgroup has
a base and a limit, defining the priority range for processes within that
workgroup. Processes will begin their Dispatcher transactions at the
base priority and decay towards the limit priority as they consume system
resources. The process priority will never drop below the limit of the
workgroup. If the boost property of the workgroup is set to oscillate,
the process priority will be reset to the base priority when it decays to
the limit priority. Processes completing Dispatcher transactions
(typically via a terminal read) are reset to the base priority.
Each of the five system-defined workgroups represents one of the five
scheduling subqueues, AS, BS, CS, DS and ES. Their only membership
criteria is the scheduling queue attribute. For example, the AS_Default
workgroup has as its membership criteria MEMB_QUEUE=AS. These workgroups
appear last in the ordered list so that the Scheduler can guarantee that
all processes will be assigned to a workgroup.
The ALTWG command allows a user to alter only the scheduling
characteristics of an existing workgroup, not the membership criteria.
As a result, there is no need for a system-wide scan since workgroup
membership does not change. (To change the name or membership criteria
of an existing user-defined workgroup, you must use NEWWG.)
ALTWG is similar in function to TUNE. In fact, if you need to adjust the
scheduling characteristics of the CS_Default, DS_Default, and ES_Default
workgroups, you may use the TUNE command (instead of ALTWG) to do so.
Altering the scheduling characteristics of a workgroup will be deferred
while a scan is in progress.
You may issue the ALTWG command from a session, job, program or in BREAK.
Pressing Break has no effect on this command. ALTWG requires System
Supervisor (OP) or System Manager (SM) capability.
NOTE Altering the scheduling characteristics of a workgroup will affect
each of the member processes. That is, the Scheduler might need to
adjust each process' priority attribute. The time required to make
these priority adjustments is related to the number of processes in
the workgroup.
EXAMPLE
To set the Program_Development workgroup's base to 158, limit to 168, and
boost priority to decay, enter:
:ALTWG Program_Development, 158, 168, , , decay
To set the Program_Development workgroup's timeslice to 500 milliseconds,
enter:
:ALTWG Program_Development ;timeslice=500
Related Information
Commands NEWWG, PURGEWG, SHOWWG, TUNE, SHOWQ, ALTPROC, SHOWPROC
Manuals MPE/iX Intrinsics Reference Manual (32650-90028)