Performance Observation and Analysis
Load Indicators
The INDICATE Command
Three commands, INDICATE, QUERY SRM, and MONITOR, provide a way to
dynamically measure system performance.
Indicate: Provides the system analyst and general user with a method to observe the
load conditions on the system while it is running. QUERY SRM: Provides the system operator with expanded observation facilities
for analyzing internal activity counters and parameters.
Monitor: Provides the system analyst and the system operator with a data collection
tool designed for sampling and recording a wide range of data. The collection of
data is divided into functional classes. The different data collection functions can
be performed separately or concurrently. Keywords in the MONITOR command
enable the collection of data and identify the various data collection classes. Other keywords control the recording of collected data on tape for later examination and
reduction.
The INDICATE command allows the system operator to check the system for
persistently heavy loads. The operator can, therefore, judge when it is best to
apply additional scheduling controls (if appropriate) or call a system analyst to per­
form an analysis of the condition by using the INDICATE, QUERY SRM, and MONITOR commands.
The system analyst has a set of operands in the INDICATE command that displays
the basic uses of and contentions for major system resources (possible bottleneck
conditions) and identifies the userids and characteristics of the active users and the
resources that they use.
Virtual machine users can use the INDICATE command to observe the basic
smoothed conditions of contention and utilization of the primary resources of
processor and storage. The INDICATE command allows them to base their use of
the system on an intelligent guess of what the service is likely to be. Over a period
of time, virtual machine users relate certain conditions of service to certain utiliza­
tion and contention figures, and know what kind of responses to expect when they
start their terminal session.
The INDICATE command allows general users and the system analyst to display at
their consoles at any time, the usage of and contention for major system resources.
General users can display usage of and contention for the major system resources
of processor and storage. They can also display the total amount of resources used
during the terminal session and the number of I/O requests. If they use the INDI­
CATE command before and after the execution of a program, users can determine
the execution characteristics of that program in terms of resource usage.
The system analyst can identify active users, the queues they are using, their I/O activity, their paging activity, and many other user characteristics and usage data.
Performance Observation and Analysis 49

The system analyst can use the data on system resource usage and contention to
monitor the performance of the system. The analyst can thus be aware of heavy
load conditions or low performance situations that may require the use of more
sophisticated data collection, reduction, and analysis techniques for resolution.
The VM/SP Scheduler maintains exponentially smoothed values for data provided
by the LOAD option. Specifically, at intervals (in seconds) depending on the
processor model, the scheduler calculates the total activities for variables such as CP and storage usage for the most recent interval, and factors them into a
smoothed wait value in the following way:
New smoothed wait value
(3 * old smoothed wait
value + current interval wait)
4
Thus, only 1/4 of the most recent interval wait is factored into the new smoothed
wait which makes it predominantly the old smoothed wait value.
The remaining INDICATE components are sampled prior to a user being dropped
from a queue. Because of the frequency of this event, the remaining components
are subject to a heavier smoothing than the wait time. A general expression for the
smoothing follows:
nsv = «rate -int) (osv) / rate) + civ
where:
nsv = new smoothing value
osv = old smoothing value
civ = current interval value (results found during the current interval (int))
int = current interval (time period being tested)
rate = either history interval (hrate) of 8 minutes, or data interval (drate) of 75
seconds
Other operands of the command allow users to obtain other performance informa­
tion that enables them to understand the reasons for the observed conditions. For
the format of the class G INDICATE command, see the VM / SP CP Command
Reference for General Users. For the format of the class E INDICATE command,
see the VM/SP Operator's Guide. Tile INDICATE FAVORED Command Page Migration I The section "Preferred Virtual Machine Options" in this publication contains
detailed information on favored execution. For information on the setting of
favored execution options, refer to the VM / SP Operator's Guide.
In order to keep· 120/0 of the preferred paging area available, CP migrates inactive
pages from preferred to nonpreferred paging areas. The preferred paging area
includes a fixed-head area and a moveable-head area. The fixed-head paging area
is paging space on a drum and/or space under the fixed heads of a DASD volume 50 VM/SP System Programmer's Guide