Performance Observation and Analysis Two commands, INDICATE and MONITOR, provide a way to dynamically measure
system performance. l!DICA!!: Provides the system analyst and general user with a method to
observe the load conditions on the system while it is running. 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.
Load Indicators
The INDICATE com.and allows the system operator to check the system for
persistently heavy loads. He can, therefore, judge when it is best to
apply additional scheduling controls (if appropriate) or call a system
analyst to perform an analysis of the condition by using the INDICATE,
and MONITOR commands.
The system analyst has a set of operands in the INDICATE com.and that
enable him to understand the basic utilizations of and contentions for
major system resources (possible bottleneck conditions) and to identify
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 utilization and contention
figures, and know what kind of responses to expect when they start their
terminal session.
THE INDICATE COMMAND The INDICATE command allows the general user and the system analyst to
display at their consoles, the usage of and contention for major system resources.
The g.eneral __ usercan display usage _of and_contenti_on __ for _ the Jlajor system resources of processor and storage. He can also display the total amount of resources he has used during his terminal session and the
number of I/O requests. If he uses the INDICATE command before and after
the execution of a program, he can determine the execution Part 2. Control Program (CP) 103
characteristics of that program in terms of resource usage.
spooling considerations, the INDICATE command may produce
results if entered while a program is issuing I/O requests.
Because of
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.
The system analyst can use the data on system resource usage and contention to monitor the performance of his system. He 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/370 scheduler maintains smoothed values of processor usage and main storage contention. Specifically, every 30 seconds, the scheduler
calculates the total wait time for the last interval and factors it into
a smoothed wait value in the following way:
(3 X old smoothed wait
value + current interval wait)
New smoothed wait value = --------------------------------
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:
(15 X old smoothed value + last
interval value)
New smoothed value = ---------------------------------
16 Other operands of the command allow users to obtain other performance
information that enables them to understand the reasons for the observed
THE CLASS G INDICATE COMMAND The format of the class G INDICATE command is:
r , ILOAQI IUSERI L J INDICATE LOAD -Produces the following response, where n is a decimal number: CPU-nnn% APU-nnn% Q1-nn Q2-nn STORAGE-nnn% RATIO-nnn The CPU figure indicates the percentage of time that the main processor is running and is derived from the smoothed wait
value maintained by the scheduler.
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