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Creating a suitable workgroup configuration that you can adjust to meet
anticipated changes in usage is the most desirable way to tune
system performance. However, situations may arise that require you
to manage your system reactively instead of proactively. Using the Workload
Manager, you can resolve system problems by adjusting the
behavior of a single workgroup or a single process. The following sections
present typical scenarios in which reactive changes are necessary. To improve a workgroup's CPU access | |
A situation may arise in which you need to give an entire workgroup
improved access to the CPU. For example, suppose it is a particularly
heavy day for orders and your telephone sales representatives need
improved response time. To improve a workgroup's access to the CPU, you can use the
ALTWG command to do any of the following:
Increase the base and limits of the workgroup to higher priorities.
Since the MPE/iX Dispatcher is priority-driven, this will give the members of
this workgroup preference over lower-priority processes.
Increase the minimum CPU percentage of this workgroup (and decrease
the minimums of other workgroups). Note that this is only effective if
the workgroup is using all of the CPU its minimum provides.
Increase the maximum CPU percentage of the workgroup (and decrease
the maximums of other workgroups). Note that this is only effective if
the workgroup has already reached its original maximum.
To degrade a workgroup's CPU access | |
A situation can arise in which you need to decrease the priority of an entire
workgroup. For example, suppose a batch run did not complete the night
before and is now impacting the response time of interactive users. Or,
perhaps a group of users is receiving 0.25 second response time when a
0.5 second response would be sufficient, making additional CPU
available to other processes. To degrade a workgroup's access to the CPU, you can use the
ALTWG command to do any of the following:
Decrease the base and limits of the workgroup to lower priorities.
Since the MPE/iX Dispatcher is priority-driven, this will give other
workgroups with a higher range of priorities preference over this one.
Decrease the minimum CPU percentage of this workgroup.
Note that this is only effective if the workgroup is already using the
CPU its minimum provides.
Lowering the CPU minimum from 25% to 20% will have no effect
if the workgroup is only consuming 15%.
Impose a maximum CPU percentage on the workgroup, or lower the existing
maximum CPU percentage, such that the workgroup is
constrained to run within a smaller percentage of the CPU allocation
than it can consume.
To modify CPU access for a single process | |
There may be occasion when you need to single out a process and
move it to a higher or lower priority. For example:
You may need to increase a process' priority if an online user
has a critical task and needs faster response time, or if a batch
job needs to finish quickly.
You may need to decrease a process' priority if it is in an
infinite loop that is critical and cannot be killed, or if a CPU intensive
process is performing a task that isn't time-critical.
To handle one process that is causing problems, do the following:
Use the NEWWG command to create a high-priority workgroup
that you will use to temporarily hold processes that require more of
the CPU. For example, to create a Hipri_procs workgroup with
the base and limit priorities set to 152, enter:
:NEWWG Hipri_procs; memb_logon="special,manager.sys";&
base=152;limit=152; position=AS_Default
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In this example, the membership criteria requires that someone log on
as manager.sys, using the job or session name special. Since the
user name and account is password-protected, it is highly unlikely that
anyone other than you could logon and gain access to this workgroup
by naturally meeting the membership criterion.
(Instead of using your own user identity in the membership criterion,
you could also create a logon that does not exist on your system.) This command includes the POSITION parameter to place the
workgroup at the end of the list of user-defined workgroups, which
minimizes scanning.
Use the NEWWG command to create a low-priority workgroup
that you will use to temporarily hold processes that are using too much
of the CPU. For example, to create a Lowpri_procs workgroup with
the base and limit priorities set to 255, enter:
:NEWWG Lowpri_procs; memb_logon="special,manager.sys";&
base=255;limit=255; position=AS_Default
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As in step one, this membership criteria is sufficiently restrictive to prevent
others from becoming natural members of this workgroup.
If necessary, enter the SHOWPROC command to identify the process whose
CPU access you need to modify.
Use the ALTWG command to move the process to the appropriate
workgroup. For example, to give a process improved CPU access, move
it to the Hipri_procs workgroup:
ALTPROC pin;WG=Hipri_procs
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Or, for example to move a CPU-bound process that is impacting other
users to a low priority, enter:
ALTPROC pin;WG=Lowpri_procs
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| | | |  | NOTE:
Another way to guarantee improved access to the CPU is
to define a larger minimum CPU value, as well as high
base and limit priorities, for the Hipri_procs workgroup.
Then, move processes to that workgroup on an “as
needed” basis. | | | | |
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