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COPYRIGHT (C) 1976, 1978, 1979 BY



                                                      Page 2

                         DEC 1979


     The purpose of this document is to provide an overview of TOPS-20
V4  and  the  TOPS-20  field  test.   It  contains  sections  with the
following information:

     1.  Introduction


     3.  Components of the TOPS-20 VERSION 4 release

     4.  References to other information


     The last field test distribution was sent in Sept.  A correction
to this was sent in October.  This current distribution includes fixes
for all the critical problems which we believe can be fixed in Release 4.
You should put this release up as quickly as you can an verify that any
problems which concerned you have been addressed.  If you have problems
please call us immediately.

     We are planning to submit TOPS-20 for general release early in
February.  Thus we need your general appraisal of this distribution
as early as possible.
TOPS-20-FIELD-TEST.DOC                                          Page 3


     TOPS-20 version 4 contains a large number  of  new  features  and
software updates.  Not only are there a large number of changes in the
monitor,  but  other  software  such  as  GALAXY,  networks,  and  IBM
communications  has  changed  dramatically as well.  This section will
describe the features in this release.

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 (via the port/channel switch) onto one of the
                system's RH20s or RH11s.

        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.
TOPS-20-FIELD-TEST.DOC                                          Page 4

        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 system).

         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.  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 libraries.

3.  Working Set Swapping

        Past performance analysis has indicated that as  the  load  on
        the  system  increases,  the  length  of time that a process's
TOPS-20-FIELD-TEST.DOC                                          Page 5

        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.

4.  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

        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.

5.  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

        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.
TOPS-20-FIELD-TEST.DOC                                          Page 6

        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 in SYSTEM:.
            There are OPR commands (not available for the first  field
            test)  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

            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 program.

6.  Dynamic Reconfiguration

        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
TOPS-20-FIELD-TEST.DOC                                          Page 7

                an appropriate SYSERR entry.

7.  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)      DN64/DN65 entries 
        3)      Tape reconfiguration entries 
        4)      Event logging from the DECnet front end
        5)      Text entries from the operator's REPORT command


        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.

9.  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.

10.   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
TOPS-20-FIELD-TEST.DOC                                          Page 8

        record  formats.      The tape mounting facility provided as a
        part  of  this  project  includes automatic volume recognition
        (AVR) in both the attended and unattended environments.

        IBM  (EBCDIC)  labeled tapes  can also  be  read.  They  cannot,
        however, be created under the tape labeling system.

11.  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

        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 Release 4.

        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.

12.   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.

13.  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 program.

        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.

14.  HASP Multileaving Support
TOPS-20-FIELD-TEST.DOC                                          Page 9

        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.

15.  Accounting Improvements

        As a part of Release 3A, TOPS-20  allowed    privileged   user
        programs  to create installation defined USAGE entries.  These
        installation defined entries can contain ASCIZ strings,  octal
        or  decimal  numbers,  date  and time values, or SIXBIT words.
        These  entries  will  be  ignored  by  all  DIGITAL   supplied
        accounting software.

        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 mounted.

        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.

16.  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  terminal.

17.  New GALAXY Functionality

        1)      Release 4 of  TOPS-20  does  not  include  the  QUENCH
                program. The remaining extra functionality provided by
TOPS-20-FIELD-TEST.DOC                                         Page 10

                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 message format.

        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 overhead.

        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 error.

18.  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

19.  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
TOPS-20-FIELD-TEST.DOC                                         Page 11

        mode  in  DUMPER  so that it can write several file pages in a
        single tape record.

20.  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 saveset.

21.  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.

22.  Support of the TV Editor

        Release  4  includes  TV  as a supported TOPS-20 editor.  This
TOPS-20-FIELD-TEST.DOC                                         Page 12

        is  a  screen  oriented  editor  that  is based on TECO.  This
        editor runs on all supported DEC  terminals  (both  video  and
        hard copy terminals).

23.  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.

24.  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.


     Before installing TOPS-20, GALAXY,  or  any  of  the  synchronous
communications   options,   the   associated   "beware"   files  (i.e.
TOPS-20.BWR) and other "doc" files should be read.  They include  last
minute updates and corrections for the specified products.

4.1  Installation Instructions

     The installation instructions for both  TOPS-20  and  GALAXY  are
contained  in  the manual "TOPS-20 Installation Guide".  This document
not only list the components necessary to install the software on your
system,  but  references the files necessary to run release 4, and the
procedures for building  a  tailored  monitor.   Before  building  any
tailored monitor, you should also read BUILD.MEM which is contained in
TOPS-20-FIELD-TEST.DOC                                         Page 13

the documentation save set of the installation tape.

4.2  Field Service Related Information

     TOPS-20 release 4 will be unfamilier to most of the field service
personnel.   In  many instances this will not be important in that the
tools used by field service (Stand alone diagnostics, SYSERR,  console
messages)  have  changed  little.   Because  problems often need to be
observed or excited during normal operation, the  following  documents
should be available for field service personnel.

     1.  TOPS-20 System Manager's Guide

         This manual provides insights into most of  the  areas  where
         change  has  taken place.  It is a good source of information
         when first approaching the system.

     2.  TOPS-20 Operator's Guide

         This  manual  contains  most  of  the  information  on  error
         recovery.   The  appendix  contains  information  on  the new
         dialogue with KLINIT and the PARSER.  This documentation also
         provides examples of the OPR command language.

     3.  TOPS-20 Operator's Command Language Reference Manual

         The new operator  command  language  is  documented  in  this
         manual.   This  document  should  be  consulted  for detailed
         information  about  the  language  or  about  any  of   OPR's

     4.  TOPS-20 DECnet-20 Programmers and Operations Manual

         This document  includes  installation,  usage,  and  checkout
         procedures.   Information  on  downline load, upline dump and
         loopback testing are in this manual.

     5.  DN200 Programmers and Operations Manual

         This  guide  includes  installation,  usage,   and   checkout
         procedures.   Information  on  downline load, upline dump and
         loopback testing are in this manual.  It should be noted that
         upline dumping is not supported during the first field test.

     6.  TOPS-20 IBM Emulation/Termination Manual

         The 2780/3780 procedures are documented in this manual.   The
         installation and checkout procedures are the same as with 3A.

     7.  *.DOC, *.BWR, *.MEM

         Field service personnel should read the  "documentation"  and
         "beware"  files  for  each of the products.  They often point
TOPS-20-FIELD-TEST.DOC                                         Page 14

         off to other sources of  information.   Of  special  interest
         would be FESTAT.MEM which describes the format of the RSX-20F
         status block and KLERR.MEM  which  describes  the  new  KLERR
         output format.  Both of these are on the documentation of the
         TOPS-20 tape.

     8.  Network Event Logging

         Because network event logging  will  not  be  supported  with
         SYSERR  in  the  first  field  test  distribution,  a special
         program EVENTS.EXE is  being  distributed  to  DECnet  sites.
         When  run,  this program will type out on a terminal, much of
         the same information which will ultimately be sent to SYSERR.
         This program and its documentation are on the DECnet tape.

     9.  OPR.HLP

         The "help" document for  the  new  operator  interface  (OPR)
         should serve as a useful (small) document once the Operator's
         Guide has been read.  It  contains  all  of  the  information
         necessary to properly enter each of the OPR commands.

    10.  User's Command Manual

         This document will be necessary for anyone using  the  system
         during  normal  operation.   If  tapes  or  disks  are  to be
         utilized, then  special  attention  should  be  paid  to  the
         sections on the MOUNT and DISMOUNT commands.