Performance Guidelines
The INDICATE command displays, at the terminal, some key information
about the system that shows the current performance indicators.
Invoking the INDICATE command displays the system conditions existing at
the time the command is issued including attached processor utilization
measurement when operating in an attached processor environment. If,
after using the INDICATE command, the system analyst wants more
extensive data collection and reduction, he can use the MONITOR command.
The user can specify automatic data collection with the SYSMON macro
in DMKSYS. Coding Considerations are contained in the section "Preparing the CP System Control File (DKKSYS)." See the !I1LJIQ for the directions on using the MONITOR command to
collect performance data on a dedicated tape drive or spool file, the
format and contents of the various classes of data collection available
with MONITOR, and details of the INDICATE command options.
Using the Performance Options
The performance of a specific virtual machine can be improved by
assigning it one or more performance options. These include: favored
execution, priority, reserved page frames, locked pages, and
virtual=real.
The performance of a VM/370 system running virtual storage operating
systems can be improved if you use virtual machine assist or Extended
Control-Program Support. The manner in which these are supported by the
various VK/370 processors is detailed below:
r , Virtual Machine Assist VM/370:ECPS 1---------------------------------------------------------------------------- 1 Standard I Feature
135-3
13A
145-3 14A 3031 3031 AP 4341 1 1 Special Feature
135
145
158
158-3 158AP 158MP 4331 1 RPQ 168
168-3 168AP 168MP 3032 3033UP 3033AP 3033MP 1 Not ,Standard IAvailablel Feature
155 155I1 165
165-3
135-3
138
145-3
148
3031
2 3031 AP2 4341 Special I Not
Feature IAvailable 4331
12
135
145
155
155II
158
158-3 158AP 158MP 165
165- 3 168AP 168MP 3032 3033 3033AP 3033MP 1 ITo function with the availability of the hardware feature. I I I L 2See the for specific VM/370: EPCS functions available on this processor.
8 IBM VM/370 Planning and System Generation Guide

Performance Guidelines
In order to invoke the favored execution, priority, reserved page
frames, and locked pages options you must have a virtual machine defined
with the appropriate command privilege classes. Usually, the operator's
virtual machine has the appropriate command classes. Additional
planning is needed to support the virtual=real option and virtual
machine assist as well as VM/370:ECPS. All of these performance options
are described in detail in the Specifying a Virtual=Real Machine
Although the virtual=real option eliminates paging, its main function is
to bypass CCW translation. This is possible because I/O from a virtual
machine occupying a virtual=real space contains a list of CCWs whose data addresses reflect the real storage addresses.
The only exception is virtual page o. Virtual page 0 does not exist
as real page 0; it is relocated to the highest page of the virtual=real
area. In order for the virtual machine to perform input/output into
virtual page 0, the CCW addresses must be translated. When CP loads an operating system into a virtual=real area, it turns
on CCW translation. Once the operating system is loaded, the operator
of the virtual machine may issue a CP command to turn CCW translation
off. When the virtual machine is operating with CCW translation off, it
must not perform I/O into virtual page O. Most operating systems can be
generated so that they do not use this area for input/output. However,
violation of this restriction may cause damage to the entire VM/370 system.
The size of the virtual=real area is specified during CP system
generation. It must be large enough to contain the entire address space
of the largest virtual machine that you execute in the virtual=real
area. Only one virtual=real area can be defined. Only one virtual machine at a time can occupy the virtual=real area. Since the virtual=real option removes pages from the dynamic paging
area, it affects the performance of the other virtual machines. The virtual=real area is set up at V!/370 initial program load (1PL). It can be released by the primary system operator to be used as part of
the dynamic paging area. Once released, it cannot be reclaimed except
by reloading VM/370. The virtual=real area must be released in total,
that is, unused pages of the area cannot be selected for release. If a very large virtual=real area is released after V"/370 initialization, a system performance degradation may occur as more and
more users log on and use the released space. The reason for this is
that the number of pages allocated for CP fixed free storage during VM/370 initialization is based on real machine size minus virtual=real
size. Therefore, the number of fixed free pages allocated for a system
with a virtual=real area may not be enough to accommodate the larger
number of users of the released space, and system overhead may increase
as CP extends to get dynamic free storage pages. Part 1. Planning for System Generation 9