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TOPS20.DOC Feb 1980
TOPS-20 Release 4
COPYRIGHT (C) 1976,1977,1978,1979,1980 BY
DIGITAL EQUIPMENT CORPORATION, MAYNARD, MASS.
The information in this document is subject to change without notice and
should not be construed as a commitment by Digital Equipment
The software described in this document is furnished under a license and
may only be used or copied in accordance with the terms of such license.
No responsibility is assumed for the use or reliability of software on
equipment that is not supplied by DIGITAL or its affiliated companies.
Release 4 of TOPS-20 is a major release of the operating system, of
GALAXY, of DECNET, of DN200, and of 2780/3780/HASP. There are
correspondingly large changes in the documentation for these software
products. The following documents are specially important sources of
information concerning release 4.
1. Software Installation Guide
Describes the software contents of the release and the
procedures for installing both TOPS-20 and GALAXY.
This file contains information which was generated after the
printed documents were "frozen" but which is vital to a
successful installation and use of the software. This covers
both TOPS-20 and GALAXY.
3. TOPS-20 System Manager's Guide
This manual provides information on the software capabilities
of the administrator for controlling and accounting for the
system usage. This manual is important in understanding many
of the new features.
4. TOPS-20 Operator's Guide
This manual contains information on the new operator interface
and how to use it. It also contains information on error
recovery and information on the updated KLINIT and PARSER
5. TOPS-20 OPerator's Command Language Reference Manual
This Manual documents the new command language. This manual
should be consulted for detailed information about this
language or about any of GALAXY's functions.
6. User's Command Manual
This manual is updated to include all the new commands
available to the user. The important areas include commands
that interact with mountable devices, and extensions to various
7. Release 4 Update Seminar and Notebook
Digital's Educational Services group will be offering a Release
4 update seminar series soon after the software is available.
They will also make available (at a price), the materials used
in the seminar for those that cannot attend. These materials
cover changes in the software and user interface; containing
information on functionality, and command and JSYS interfaces.
8. TOPS-20 DECNET-20 Programmers and Operations Manual
This document includes installation, usage, and checkout
procedures for DECNET products. Information on downline load,
upline dumping, and loopback testing are in this manual.
9. DN200 Programmers and Operations Manual
This guide includes installation, usage, and checkout
procedures. Information on downline load, upline dump, and
loopback testing are included here.
10. TOPS-20 2780/3780/HASP Emulation/Termination Manual
The procedures for the installation and running of the IBM
communications products are documented in this manual.
11. *.BWR and *.DOC, *.MEM files for various products
These files (contained on the distribution tapes) contain
important information on features and restrictions which are
not contained in normal documentation. It is important to read
these before attempting to do an installation.
The file ACJ.MEM is an example of the access control mechanism
which should serve as a basis for any site desiring to utilize
Installation of Software
This is a tightly coupled release. TOPS-20, DECNET, DN200 and
2780/3780/HASP all utilize the new GALAXY features and functionality.
Because of this, you cannot mix R3A components with R4 components. You
CANNOT, for instance, put up R4 with the 3A GALAXY system because some
of the functionality has moved from the EXEC to OPR. Likewise both
DECNET and the 2780/3780 count on both GALAXY and monitor features of
their respective releases.
You CAN, however, run both R3A and R4 from the same disk packs. Thus it
is possible to put up R4 for training and experimentation, and revert to
R3A for production until you are ready to utilize R4 full time.
New Features In Release 4 -------------------------
The rest of the document covers New features, changes, and performance
considerations for release 4 users.
Major TOPS-20 Release 4 Features
TOPS-20 Release 4 contains many new features for administrative,
operations personnel, and users. While there have been many additions
to the system, the normal user will see little change in his/her use of
the system except where new features are employed. Administrative and
operations personnel, on the other hand, will find that their command
interface to the system has changed greatly in a manner which provides
many new facilities, full command recognition, and an integrated
approach to operator software, but which is (alas) different.
Several projects in Release 4 were designed to provide mechanisms
for the site administrator to "tune" the performance characteristics of
the system. Other projects were to improve the communications
facilities in both DECNET and IBM communications products. And still
others were to provide more operations and administrative control over
the system. The following is a listing of the major components in
TOPS-20 Release 4.
! New Features for the Site Administrator !
1. Directory and Program Name Cache
Release 4 of TOPS-20 will keep a cache of the last few referenced
directories. This will tend to reduce the number of page faults
required to look up files. This project does not change the user
interface to the system in any way.
Another type of cache being kept is the Program Name Cache. The
names of often used programs and libraries can be placed in the
file SYSTEM:PROGRAM-NAME-CACHE.TXT. At startup, the system will
map each of the libraries (via a program called MAPPER.EXE) and
will reserve an OFN for each of the programs. The effect of this
is to decrease the startup time of programs and the access time to
2. Working Set Swapping
Past performance analysis has indicated that as the load on the
system increases, the length of time that a process's working set
stays in memory after it blocks decreases. This causes the process
to fault in more of its working set pages from the swapping space
once it is unblocked. Swapping a process's working set causes all
the pages to be written onto a contiguous area of the swapping
space. Then, when the process becomes runnable again, the monitor
will read in the entire working set at once.
3. Reduction in Scheduler Overhead Due to Excessive Terminal Wakeups
In order to reduce the scheduler overhead incurred by the EXEC or
other terminal oriented processes, Release 4 provides a mechanism
for a process to specify an arbitrary set of wake up characters.
For instance this allows the EXEC to wake up only on a question
mark, and not on all punctuation. This should decrease the number
of times the EXEC gets scheduled during the typing of a command.
Another aspect of this feature is the ability to wake up when a
field of a desired length has been entered even though a break
character has not been entered.
Programs which use the wake up character masks in order to respond
to a particular character or which read field by field should be
changed to use these features as a means of decreasing system
loading. Programs which use the TEXTI JSYS will automatically take
advantage of this feature.
4. Scheduler Controls
TOPS-20 Release 4 will provide the system administrator with a set
of scheduler controls that can be used to tune the system to run
with the desired characteristics for that installation. The
following methods for controlling the scheduler are available:
1. Bias control
A bias control has been added which allows the system
administrator to favor either interactive users or
computational users. The control mechanism can be set to a
value between 1 and 20. When the bias is set to 1, the system
will maximally favor interactive users over computational
users. When the bias is set to 20, the system will maximally
favor computational users. There is a command to the OPR
program which allows the operator to specify the setting of the
2. Class scheduler
The class scheduler allows the system administrator to specify
the percentage of CPU time (share) that any class of users will
receive. There are two ways of placing users into classes.
One method is to associate a class number with each valid
account on the system. When the user logs in, or changes the
account, the associated class will take effect. The other
method is to set the class via the "Access Control Job" (see
item 20). When a job logs in, the access control job (ACJ) has
the opportunity to associate a class with that job. Thus the
site can program the ACJ to provide any mapping of users to
classes which are meaningful.
The 'share' of the processor assigned to each class is
initially specified in the 4-CONFIG.CMD file. There are OPR
commands which allow the operator to change the share assigned
to each class. Another parameter which can be specified is
whether or not the system should allocate the unused portion of
a class's share (the windfall) to other users. This parameter
is also initially set in 4-CONFIG.CMD.
One simplified use of the class scheduler is to place all batch
jobs in one class and all terminal originated jobs in another.
This provides a method for regulating the percentage of CPU
time received by these two different types of users.
3. High Priority Queue
A special high priority queue has been defined which is
searched before the interactive queues. A process must be
explicitly placed in this queue. This should be done only for
processes that need high priority scheduling and which does not
compute for long periods of time. Normally programs which
provide services to other jobs should be assigned to this
queue. The access control program is an example of such a
5. Enhanced System Performance Reporting
The WATCH program has been enhanced during Release 4 to print out
more system performance statistics. Included in the new
information reported by WATCH is:
1. The working set size of each job,
2. The number of page faults taken by each job,
3. The average time to satisfy those page faults,
4. The number of wake ups for each job,
5. The average time to service each wake up,
6. The active swapping ratio of the system, and
7. The disk seeks, reads, and writes per spindle.
This version of WATCH includes the capability of the program FRIDAY
which was distributed with 3A.
6. Error Logging
The following additional entries are being added to SYSERR to
provides better information for field service.
1. KMC11/DUP11 entries on the KL systems
2. Tape reconfiguration entries
3. Event logging from the DECnet front end
4. Text entries from the operator's REPORT command
7. Accounting Improvements
Release 4 enters tape mounting information into the USAGE file.
This information includes the name of each volume that was mounted,
the name of the user issuing the mount request, the length of time
that the tape was in use, and the number of characters read and
written during the time that the tape was mounted.
Release 4 enters structure utilization information into the USAGE
file. These entries contain the structure name, the user's account
string, and the length of time that the user had the structure
Release 4 also implements a mechanism for the system administrator
to close out one shift and start another shift. This allows the
system administrator to charge differently for prime shift versus
second or third shifts. This has been done by implementing a new
USAGE JSYS function. There is a mechanism by which the system
administrator can specify the times of the day of all shift
changes. The system will automatically execute the change shift
function at each of the specified times.
Other changes include a new entry which has been added to support
file Archiving, and charging the printing of a batch LOG file to
the user and not to BATCON.
8. Access Control Mechanism
An access control mechanism has been added to TOPS-20 in Release 4.
This mechanism will allow each installation to write an access
control program to carry out that installation's policies regarding
privileges and resource assignment. Some of the resources that can
be controlled by this facility are:
1. Device assignment,
2. The enabling of capabilities,
3. Creating jobs with CRJOB,
4. Logging into the system,
5. Logging off the system,
6. Creating processes (after Nth process),
7. Setting terminal baud rate,
8. Setting of ENQ quota,
9. Directory creation or modification,
10. Structure mounting,
11. Access to MDDT,
12. Verification of scheduler class assignment, and
13. Access to given labeled magnetic tapes.
An example program "ACJ.MEM" is being distributed with release
four. This program illustrates many of the techniques which should
be incorporated in a successful access control program. This
example program is not a full fledged ACJ in that it does not
restrict access to any resource. It merely logs all such requests
and then grants the access. It is, however, a good prototype which
serves as an illustration of how to write a program which utilizes
the access control mechanism and which protects itself from most of
the calamities which can befall a job running on the system. It is
expected that most sites will extend this program to meet their
individual needs. The program will be in the documentation
9. RAMP Projects
As part of a continuing effort to increase the availability of the
DECSYSTEM-20, a large amount of effort has gone into RAMP features
(Reliability and Maintainability Program). Many of these result in
different output to SYSERR, and the CTY during error conditions.
In general, they are invisible to users during normal operating
conditions. The operator, however, will notice slight changes in
the dialogue when bringing up the system. RAMP features are being
included in both TOPS-20 and the RSX20F front end system.
! New Features for the Operator !
1. Dynamic Recognition of Disk and Tape Drives
The Release 4 monitor will automatically note whenever a disk drive
or a tape drive or a tape controller is added to the system
configuration. It will then create the necessary internal data
base to allow these new units to be accessed by the timesharing
users. This dynamic recognition will take place without having to
reload the TOPS-20 monitor.
The situations which would activate this dynamic recognition happen
on the first interrupt after one of the following:
1. A disk drive that was not connected to an RH20 or RH11 on the
system when the monitor was initially loaded is switched on
(via the port/channel switch).
2. A disk drive that was completely powered off at the time the
monitor was loaded is powered on.
3. A tape drive whose logic was powered off at the time the
monitor was loaded has its logic powered on.
4. A tape controller that was powered off at the time of the
loading of the monitor is powered on.
This project allows two DECSYSTEM-20's to share the same disk
drives in the following manner. Configure the hardware such that
each of the shared disk drives has one port connected to an RH20 on
the first system and has the other port connected to an RH20 on the
second system. The port switches for all of the shared disk drives
MUST be set to either the Port A or to the Port B positions but NOT
to the A/B position. When a structure is to be mounted on a
particular system, the following procedure should be followed:
1. With the drive powered down, set the port switch to either the
'A' or 'B' position (whichever connects it to the desired
2. Mount the desired disk pack on the drive.
3. Power up the disk drive.
At this point the TOPS-20 system will notice that the disk drive is
on-line and will make it available to the system.
This project is NOT intended to provide a completely general disk
sharing facility between two systems. For instance, if the drive
is left in the A/B position, then both systems might try to access
the drive which WOULD LEAD TO THE DESTRUCTION of the data on any
structure mounted on that drive.
2. Dynamic Reconfiguration of MOS Memory and the Tape Subsystem
1. When the system contains MOS memory, a system program is run
which responds to memory errors. This program's name is TGHA
and runs unattended much in the manner of DDMP. The TGHA
program can take failing memory off- line and can perform
"spare bit substitution".
2. There is a new OPR/ORION command added as part of the tape
labeling project to take on or off-line any of the magtapes on
the system. This command will make an appropriate SYSERR
3. New GALAXY Functionality
1. Release 4 of TOPS-20 does not include the QUENCH program. The
remaining extra functionality provided by QUENCH under Release
3 has been moved into the EXEC. This includes the support for
the DN64/DN65 commands for submitting jobs to an IBM system and
support for releasing deferred spool files.
2. The EXEC has been changed to support the Release 4 GALAXY
3. There is a new GETJI/SETJB function to mark that a job is at
command level. The EXEC and PA1050 use this JSYS to tell
BATCON when the job is at command level.
4. The TOPS-20 monitor keeps a Batch Stream Number for each batch
job on the system and to allow the operator to permit or
inhibit communication between a batch job and the operator.
5. A large change in the operator interface has taken place.
Instead of controlling the system environment by talking
directly to the various system programs, the operator now works
thru a unified mechanism which is provided by the OPR/ORION
interface. The operator communicates through a unified command
language to the OPR program which in turn communicates with the
ORION program to carry out the required actions.
6. The GALAXY components now run "native mode" on the
DECSYSTEM-20. This improves their performance and lowers their
7. A log file is kept by the ORION program into which all GALAXY
operator message traffic is stored. In the case of a fatal
error (stopcode) occurs in a GALAXY component, a large amount
of information is recorded here and on the terminal. This
information is extremely helpful to someone analyzing the
4. Increased Tape Utilization by DUMPER
Currently DUMPER writes 518 word records on tape (1 file page plus
6 header and checksum words). Since Release 4 will support two
tape drives capable of writing data at 6250 CPI, using DUMPER on
these tape drives would mean that approximately half of the tape
would be wasted in inter-record gaps. To reduce this wastage and
to increase the amount of data stored on a tape, we are
implementing a record blocking mode in DUMPER so that it can write
several file pages in a single tape record.
! New Features for the User !
1. The SWTRP JSYS
In order to reduce the time that it takes an OTS to service an
arithmetic or a floating point overflow, we have implemented the
SWTRP JSYS to let user programs set the trap words in the user page
table (UPT). This will allow the process to trans- for control
directly to the user program to service the over- flow condition.
2. ANSI Tape Label Support
The Release 4 tape label facility provides for level 4 tape label
verification and creation according to the ANSI Tape Label
standard. The tape label facility provides for multi-file volumes
and multi-volume files. The facility also provides record
processing of fixed, variable, and spanned record formats. The
tape mounting facility provided as a part of this project includes
automatic volume recognition (AVR) in both the attended and
IBM (EBCDIC) labeled tapes can also be read. They cannot, however,
be created under the tape labeling system.
3. DECnet Task-To-Task Support Increased
Release 3A of TOPS-20 supported DECnet-20 Task-to-Task
communications. Any DECSYSTEM-20 or DECSYSTEM-2020 can be
connected to the following other DECnet products: RSTS, RT-11,
RSX11/M, IAS, VAX, DECSYSTEM-2040, 2050, 2060, or a DECSYSTEM-2020.
In Release 3A, the DECSYSTEM-2040, 2050, or 2060 systems could
support up to one DECnet Task-to-Task link. This limitation has
been raised to eight links in Release 4. A DECSYSTEM-2020 can
support up to two lines for Task-to-Task in both Release 3A and
A Network File Transfer Facility is available with Release 4 which
will enable users to easily pass files between systems which are
connected with DECnet.
4. New Leader Format for the ARPANET Protocol
The ARPANET Protocol was originally designed with a limit of 64
IMPs on the network. Recently this limit was reached and the
protocol was modified to make it possible to address more than 64
IMPs. Release 4 of TOPS-20 incorporates the changes necessary to
support this new leader format.
5. Execute Only Capability
Release 4 of TOPS-20 supports the "Execute Only" protection of
files. Specifically, an executable file (program.EXE) can be given
an "Execute Only" protection. That file can then be executed via
the "R" or "RUN" commands. However, that file cannot be copied, or
read; and the program cannot be saved, examined, modified, mapped.
Likewise, the monitor will not allow DDT or user versions of the
Compatibility Package merged into the address space of that
A limitation of the Execute Only facility is that an "Execute Only"
program cannot merge any other "Execute Only" programs into its own
address space. This means that an "Execute Only" program cannot
call an "Execute Only" object time system nor can it map in any
"Execute Only" overlays.
6. HASP Multileaving Support
The DN60 software has been extended to provide not only 2780/ 3780,
but also HASP Multileaving support. This will allow multiple
devices to be active concurrently, will provide remote station
console support, and will permit convenient operator enquiry from
the remote station.
7. Remote Job Entry Station (DN200)
Release 4 of TOPS-20 supports a PDP-11 based remote job entry
station. OPR, LPTSPL, and CDRIVE running on the -20 communicate to
the remote PDP-11 using a DECnet-20 Task-to-Task link. There are
tasks running in the PDP-11 to drive the LPT, CDR, and the console
8. The EXEC Interface to the COBOL-68 and COBOL-74 Compilers
The EXEC has been enhanced to let the user specify which COBOL
compiler is to be used during the compilation of any COBOL program.
9. More Efficient Asynchronous Terminal Support
Overhead for asynchronous terminal support has been reduced.
Coupled with an improvement in XON/XOFF handling, users should find
that terminal-bound applications run more efficiently.
10. Support of the TV Editor
Release 4 includes TV as a supported TOPS-20 editor. This is a
screen oriented editor that is based on TECO. This editor runs on
all supported DEC terminals (both video and hard copy terminals).
11. File Archiving
Release 4 also includes a file archiving system. This system is
based on DUMPER. The archiving system is capable of running in
both an archiving mode and a virtual disk mode.
The file archiving system will allow users to request that files be
archived onto tape. The data in these files can then be deleted
from the disk, freeing up valuable disk space. The contents of the
files can be recalled from tape at any time in the future. This
recall can be done by explicit request or automatically when the
file is opened.
TOPS-20 Release 4 User Interface Changes
TOPS-20 Release 4 User Interface Changes
The following reflect many of the changes in the TOPS-20
interface seen by administrators, operators, and normal users. In
most cases, the normal user will not be severely impacted by the
changes in that most are additions to existing functionality. The
impact will be greatest on the administrator, operator and those
users who utilize the tape system.
o Class Scheduling
-- CONFIG.CMD file
-- BATCH-CLASS n (class for batch jobs)
-- CREATE n m (sets class' (n) CPU share (m%))
-- ENABLE CLASS-SCHEDULER (turns on class schedulER)
-- (in OPR)SET SCHEDULER CLASS n (TO) m (percent)
-- (in OPR)SET SCHEDULER BATCH-CLASS n
-- (in OPR)ENABLE CLASS-SCHEDULER ....
-- (in OPR)DISABLE CLASS-SCHEDULER
o Bias Control
-- CONFIG.CMD file
-- BACKGROUND (run batch jobs on lowest queue)
-- BIAS n (initial setting of bias control)
-- (in OPR)SET SCHEDULER BIAS-CONTROL (TO) n.
o Access Control
-- Access Control Program written to meet local sites
o 4-CONFIG.CMD file choices
-- CHANGE (ACCOUNT SHIFT AT) <time> (ON) <days>
-- ENABLE TAPE DRIVE ALLOCATION (users to utilize
MOUNT command for some or all tape drives).
-- ENABLE WORKING-SET-PRELOADING
-- TAPE-RECOGNITION-ERRORS <action> (unload or assume
unlabeled when wrong tape mounted).
-- TAPE-RECYCLE-PERIOD (for migration)
o Command Interface (no detail given here)
-- Fundamentally changes the interface from one where
the operator converses with each individual operations
task, to an integrated interface where a specialized
executive (OPR) provides a consistent command language
for interacting with operations tasks.
--New Functionality in DUMPER
TOPS-20 Release 4 User Interface Changes
o Labeled Tapes
--New Commands (in OPR)
--More controlled environment
o Changes in Error Output
--Additional Bug(hlt,chk,inf) information
--More CTY information on KL failure
o Mountable Device Interfaces (disk/tape)
-- ASSIGN (cannot use for controlled device)
-- DEASSIGN(cannot use for controlled device)
-- MOUNT request(supercedes TMOUNT/SMOUNT)
-- DISMOUNT request
-- REWIND (includes current tape or volume set)
-- UNLOAD (illegal for MOUNTed devices)
o Archived Files
-- ARCHIVE Command
-- RETRIEVE Command
-- SET RETRIEVAL-WAIT (for offline files)
-- Potentially smaller directories
-- CANCEL (ARCHIVE) request
-- DELETE filespec,
ARCHIVE (files included) CONTENTS (only)
o Other Command Enhancements
-- COMPILE /LANGUAGE-SWITCHES:(..)/74-COBOL
-- similar LOAD and EXECUTE
-- COPY (byte size settable)
-- CREATE/EDIT (set default editor)
-- INFORMATION (several items updated)
-- PRINT (and related commands)(new and
-- SET DEFAULT (new options)
-- SET FILE (new options)
-- SET LOCATION <node> (new option)
-- SYSTAT (new options)
-- TERMINAL (MODE IS) (new options)
o TV screen editor support
-- Expanded number of nodes (on 2040/2050/2060)
-- Network File Transfer Program
-- COPY, DELETE, DIRECTORY, SUBMIT commands
-- New addition of HASP capability
-- New Spooler
-- Commands all interpreted by the EXEC
Performance Considerations With Release 4
Performance Considerations With Release 4
In release 4, a greater emphasis has been placed on providing good
interactive responsiveness than was placed on this in 3A. There have
been a number of projects including:
1. Increasing the terminal output rate.
2. Providing a more controlled breakset to eliminate unneeded
wakeups (and scheduling overhead).
3. Redefining the scheduler queues to provide a "very interactive"
and a "was just very interactive" queue.
4. Tuning capability using the bias control.
5. Interactive priority even with class scheduling.
There is no across the board increase in performance with release 4 as
compared to release 3A. In general, some components will run faster at
the expense of others. In a system that is running at full capacity,
there may be a a decrease in throughput accompanying an increase in
responsiveness. The bias control and the class scheduler are provided
as tools to allow you to bias the system to your needs.
In order to provide the new functionality in release 4, a lot of
code and some new tables were added, tables were expanded, and system
defaults were changed. Significant increases were made in the defaults
governing the amount of swapping space allocated (NDST) and the number
of open files (NOFN). These increases were made because of evidence
that both program size and file usage are increasing at many customer
sites. The sum of these increases adds about 20 pages to the resident
monitor (including 8 pages for increased swapping space). The
non-resident portions of the monitor have also grown as as functionality
was added. The effects of these increases will be:
1. Less memory available for user tasks.
2. More swapping necessary to sustain current load.
3. Performance on systems which are paging heavily under 3A may be
worse. Tuning will often help, but on small systems (less than
256K) with heaving paging, it may not be able to compensate for
the loss of memory. In these cases, it is often possible to
use the class scheduler to increase the performance of certain
classes of users at the expense of others; however total
system performance may still remain at less than 3A levels.
Performance Considerations With Release 4
SUMMARY OF WHAT GREW IN TOPS-20 RELEASE 4.
-- Resident Monitor Requires More Dedicated Space
-- More Code Added
-- Larger Defaults For:
-- Swapping Area
-- Number of OFN's
-- Larger entry's required in:
-- Job tables
-- Process tables
-- Terminal tables
-- Added Caching of Information
-- Larger Non-resident Monitor
-- More Code Added
-- More Per-Process Information
-- More Per-Job Information
-- More Per-Terminal Information
-- Increase of about 12 pages with same amount of swapping space.
-- Mapping additional swapping space requires about 8 pages more.
-- Directories hold potentially fewer files because of Archiving
Performance Considerations With Release 4
SUMMARY OF FEATURES RELATED TO PERFORMANCE/TUNABILITY
-- Working Set Preloading
-- Scheduler Controls
-- Class Scheduler
-- Bias Control
-- Interactive Responsiveness Increased
-- Optimized breakmask lowers EXEC overhead
-- Terminal throughput increased
-- New Scheduler Queues
-- Directory and Name caches, find commonly used
objects with less overhead
-- GALAXY runs without PA1050 (Native Mode)
-- WATCH Helps Pinpoint Resource Usage
-- New System Variables
-- "FRIDAY-like" per job data
Performance Considerations With Release 4
USING THE TUNING TOOLS TO ENHANCE PERFORMANCE
1. When interactive users are most important
1. Have batch jobs run on lowest queue (CONFIG.CMD)
2. Have batch jobs put in special class(CONFIG.CMD)
3. Use bias control to do "disaster avoidance" (stops
scheduling computational users when interactive load
average reaches a certain threshold.)
4. Experiment with working set swapping (CONFIG.CMD) to
determine if it helps. (It has proven to decrease the
number of disk seeks in some workloads). It may increase
2. When there is a high priority process (like a file update
program which communicates with other programs
1. Put that program in the high priority queue.
2. Put associated programs in a class with a high percentage
3. Put other users in a class with a lower percentage.
3. When groups of users have different importance
1. Put users in scheduling classes on a group basis.
2. Allocate appropriate shares to classes.
3. Put operations jobs in another class.
4. When trying to increase across the board performance
1. determine if working set swapping helps.
2. Determine which setting of the bias control is best.
3. Put users in classes based on user profile (good vrs the
4. Write a program to change bias and/or class targets based
on local heuristics.
5. Use WATCH to determine if disk traffic is balanced, to
monitor users with large requirements, and to spot trends.