f- OpenVMS FAQ -&- page 4)b @5z

HP OpenVMS Systems Documentation

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The OpenVMS Frequently Asked Questions (FAQ)


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3.3 How do I extract the contents of a HELP topic to a text file?



ETo extract all the text of a HELP topic (and its subtopics) to a text@file for perusal with a text editor, printing out, etc., use thefollowing command:

 

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2$ HELP/OUT=filename.txt help-topic [help-subtopic]




BIf the help text you want is not in the standard help library (forCexample, it's help for a utility such as MAIL that has its own helpGlibrary), add /LIBRARY=libname after the HELP verb. To see the names of5help library files, do a directory of SYS$HELP:*.HLB.h

3.4 Does OpenVMS Marketing have an e-mail address?



GYes - if you can't get the answers to marketing questions elsewhere, if;you have comments or complaints about OpenVMS, send mail toBopenvms-info{atsign}hp.com. This address is not a support=channel, and is solely intended to provide informal method to7communicate directly with members of OpenVMS Marketing.o

3.5 Where can I learn about OpenVMS executive internals?



GThe OpenVMS Internals and Data Structure manual (IDSM) explains how theEOpenVMS executive works. The book covers the operating system kernel:Aprocess management; memory management; the I/O subsystem; and theGmechanisms that transfer control to, from, and among these. It gives anEoverview of a particular area of the system, followed by descriptionsCof the data structures related to that area and details of the codethat implements the area.

GThe first edition of the OpenVMS Alpha internals book describes VersionE1.5. Although there have been several releases of OpenVMS Alpha sinceFVersion 1.5 (V6.1, V6.2, V7.0, V7.1, etc) and many details in the bookCare no longer accurate, it continues to provide a strong conceptual!description of OpenVMS internals.

=This book has been split into five pieces, each to be updated?separately. The first such volume, published in early 1997, wasD"OpenVMS Alpha Internals and Data Structures: Scheduling and Process=Control," which covers the Version 7.0 implementation of true;multithreading and the changed scheduling model it implies.

<The internals books are available through Digital Press, see?Section 3.6w

3.6 Where can new users find tutorial information about OpenVMS?



FFirst, see if your local site has information on this topic. Each siteGcan have site-specific features and configuration. Some sites will haveFsite-specific new user's documentation, covering various site-specific?things that are difficult or impossible for the general OpenVMSdocumentation to cover.7

3.6.1 Tutorial Websites?



Various websites with OpenVMS information are available; Table 3-2 contains some suggested URLs.

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Table 3-2 OpenVMS Tutorial and Documentation Websites
URL Sponsor
# Introductory
J / http://www.levitte.org/~ava/vms_faq.htmlx
J / http://saf.bio.caltech.edu/vms_sheet.html
Y > http://seqaxp.bio.caltech.edu/www/vms_beginners_faq.html
  $ Various introductory materials
G , http://www.montagar.com/openvms_class/
  L Members of the Encompass DFWCUG maintain a website with many materialsM available, including an Overview of OpenVMS, an Introduction to DCL andJ the TPU Editor, Advanced DCL Command Procedures, OpenVMS Operations:K Batch, Print, Tape, an Introduction to OpenVMS Management, to OpenVMSL User Management, to OpenVMS Network Management, and to OpenVMS ClusterI Management. These training materials have been presented at various DECUS symposia.
T 9 http://www.mcsr.olemiss.edu/unixhelp/VMStoUNIX.html
  I A comparison table of various command-level tasks, with information % % % M on the UNIX and Linux shell command(s), and on the OpenVMS DCL command(s).
/ HP OpenVMS Documentation
B ' http://www.hp.com/go/openvms/doc/
  F Various introductory guides as well as more advanced manuals areE available in the OpenVMS and layered product documentation set.
* HP OpenVMS Training
M 2 http://h18000.www1.hp.com/training/home.html 
M 2 http://www.openvms.compaq.com/wbt/index.html
  K HP offers training information and Technical Resource Kits (TRKs) andL other Training for OpenVMS. An OpenVMS certification (testing) program is also available.
Z http://www.jcameron.com/vms/
   An OpenVMS Quiz
R http://www.CCSScorp.com/
  > CCSS Interactive Learning has OpenVMS training materials
R http://www.acersoft.com/
  ? AcerSoft Training information, and Shannon Knows Punditry
N http://www.mindiq.com/
  ! MindIQ training information
T http://www.quadratrix.be/
  J Quadratrix; OpenVMS training, products and services; affiliated with! Global Knowledge and KeyJob
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3.6.2 Books and Tutorials?



BSome of the OpenVMS books that are or have been available from theDigital Press imprint



Ware listed in Table 3-3:

S  +                                               
Table 3-3 DP Books
Title and Author ISBN
A Getting Started with OpenVMS System Management, 2nd Edition%
David Donald Miller, et al
 1-55558-243-5
* Introduction to OpenVMS, 5th Edition
Lesley Ogilvie Rice
 1-55558-194-3
 Introduction to OpenVMS
David W Bynon
 1-878956-61-2
= OpenVMS Alpha Internals: Scheduling and Process Control  1-55558-156-0
< OpenVMS AXP Internals and Data Structures: Version 1.5  1-55558-120-X
% OpenVMS System Management Guide
Baldwin, et al
 1-55558-143-9
. The OpenVMS User's Guide, Second Edition
Patrick Holmay
 1-55558-203-6
( Using DECwindows Motif for OpenVMS
Margie Sherlock
 1-55558-114-5
8 VAX/VMS Internals and Data Structures: Version 5.2  1-55558-059-9
2 Writing Real Programs in DCL, Second Edition&
Hoffman and Anagnostopoulos
 1-55558-191-9
/ Writing OpenVMS Alpha Device Drivers in C!
Sherlock and Szubowicz
 1-55558-133-1


EFor various featured OpenVMS books, also please see the books link atthe OpenVMS website:



8For a bibliography of various OpenVMS books, please see:

d

3.7 What OpenVMS mailing lists are available?



GVarious OpenVMS mailing lists are available, with some of the availableXlists detailed in Table 3-4.

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Table 3-4 OpenVMS Mailing Lists
Subscription Interest Area
0 OpenVMS Freeware archive announcement list  FSupdate@goatley.com'
FSupdate-request@goatley.com 1
& Two-way echo of vmsnet.internals " VMSnet-Internals@goatley.com/
VMSnet-Internals-request@goatley.com 1
) OpenVMS Alpha Internals discussions  Alpha-IDS@goatley.com(
Alpha-IDS-request@goatley.com 1
 BLISS discussions  BLISSters@goatley.com(
BLISSters-request@goatley.com 1
; Process Software MultiNet mailing list (news gateway)  Info-MultiNet@process.com,
Info-MultiNet-request@process.com 1
: Process Software TCPware mailing list (news gateway)  Info-TCPware@process.com+
Info-TCPware-request@process.com 1
7 Process Software PMDF mailing list (news gateway)  Info-PMDF@process.com(
Info-PMDF-request@process.com 1
H The Software Resources International (SRI) CHARON-VAX VAX emulator package % M % 4 " CHARON-VAX-Users@process.com/
CHARON-VAX-Users-request@process.com_ 1
0 Info-Zip's Zip & UnZip discussion list  Info-Zip@wku.edu
 ' Info-Zip-Request@wku.eduw 1
? RADIUS-VMS, a RADIUS server for OpenVMS discussion forumP  radius-vms@dls.net%
radius-vms-request@dls.netc 1
7 Internet Service Providers (ISPs) running OpenVMSl  vms-isps@dls.net#
vms-isps-request@dls.netp 1
F Users of Mark Daniel's WASD web server for OpenVMS VAX and AlphaF exists. Information about this list server and details on how toD subscribe to the list are available at the referenced website. P http://wasd.vsm.com.au/
 VMS Foruma W 1< http://www.neurophys.wisc.edu/comp/ava/vms_forum.htmlx



G1This is the subscription address. Usually, you will want toaAsend a mail message with no subject line, and a SUBSCRIBE or HELPr(command in the body of the mail message.

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3.8 What is this Ask The Wizard website I've heard about?



f#The HP OpenVMS Ask The Wizard (ATW)nEwebsite was an informal area discussing OpenVMS, containing questions (and answers on a wide variety of topics.

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fGFor additional information on the OpenVMS Ask The Wizard (ATW) area andAfor a pointer to the available ATW Wizard.zip archive, please sees@Section 3.8.

h6To access a cited topic directly, use the URL filenameGWIZ_topic-number.HTML, or use the topic search engine. Cited topics areiEshown in parentheses, and act as unique topic addresses. These should Fnot be confused with the relative topic numbers shown at the site. For@example, the topic (1020) can be accessed directly using the URLGfilename wiz_1020.html, at the web site that the following URL resolvesdinto:h



nGA zip archive (named wizard.zip) containing all of the available topics Band questions can be downloaded from the above URL. The wizard.zipE zip archive is completely regenerated when/if existing topics posted,F out to the ATW website are updated. Copies of this wizard.zip archive: also generally ship out on the OpenVMS Freeware, as well.

dDNew (informal) questions and discussions are now being directed awayfrom the ATW area to the; ITRC area, and specifically to the ITRC discussion forums:a

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3.9 Where can I find the latest C run-time library manuals?



CThe C run-time library (RTL) reference documentation has been movedsGfrom the C language documentation set to the OpenVMS documentation set.dFFor the most recent version of the C RTL documentation and the OpenVMS3standard C library, please see the OpenVMS manuals.t

gEIn addition to the user-mode C RTL, there is a second kernel-mode RTLaFaccessable to drivers on OpenVMS Alpha and OpenVMS I64. For details onBthis second library and on the duplicate symbol errors that can be3triggered when this library is referenced during antyincorrectly-specified LINK command, please see Section 10.22.1. For.Bgeneral information on this kernel RTL, see the Digital Press book@Writing OpenVMS Device Drivers in C. For details, please see the0associated OpenVMS source listings distribution.



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Chapter 4
Time and Timekeeping

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If you are searching for something here, please(consider using the text-format FAQ.



eFThis chapter discusses time, timekeeping, system time synchronization,1clock skew and clock drift, implications of usingr5SUBMIT/AFTER=TOMORROW, and other time-related topics.j

4.1 A brief history of OpenVMS Timekeeping, please?



hFWhy does OpenVMS regards November 17, 1858 as the beginning of time...

fAThe modified Julian date adopted by the Smithsonian Astrophysical Observatory (SAO) /for satellite tracking is Julian Day 2400000.5,t4which turns out to be midnight on November 17, 1858.

hFSAO started tracking satellites with an 8K (nonvirtual) 36-bit IBM 704Cin 1957 when Sputnik went into orbit. The Julian day was 2435839 on FJanuary 1, 1957. This is 11225377 octal, which was too big to fit intoAan 18-bit field. With only 8K of memory, the 14 bits left over by Fkeeping the Julian date in its own 36-bit word would have been wasted.GSAO also needed the fraction of the current day (for which 18 bits gave=Eenough accuracy), so it was decided to keep the number of days in thecHleft 18 bits and the fraction of a day in the right 18 bits of one word.

>Eighteen bits allows the truncated Julian Day (the SAO day) toDgrow as large as 262143, which from November 17, 1858, allowed for 7Gcenturies. Possibly, the date could only grow as large as 131071 (usingrF17 bits), but this still covers 3 centuries and leaves the possibilityEof representing negative time. The 1858 date preceded the oldest starrGcatalogue in use at SAO, which also avoided having to use negative time .in any of the satellite tracking calculations.

dDThe original Julian Day (JD) is used by astronomers and expressed in=days since noon January 1, 4713 B.C. This measure of time wascAintroduced by Joseph Scaliger in the 16th century. It is named in.+honor of his father, Julius Caesar Scaliger @(note that this Julian Day is different from the Julian calendar4that is named for the Roman Emperor Julius Caesar!).

GWhy 4713 BC? Scaliger traced three time cycles and found that they were Eall in the first year of their cyle in 4713 B.C. The three cycles are_F15, 19, and 28 years long. By multiplying these three numbers (15 * 19F* 28 = 7980), he was able to represent any date from 4713 B.C. through 3267 A.D.t

oBThe starting year was before any historical event known to him. InCfact, the Jewish calendar marks the start of the world as 3761 B.C.=DToday his numbering scheme is still used by astronomers to avoid theCdifficulties of converting the months of different calendars in useoduring different eras.

The following web sites:

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Fare all good time-related resources, some general and some specific toOpenVMS.O

4.1.1 Details of the OpenVMS system time-keeping?

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4.1.1.1 VAX hardware time-keeping details...

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4.1.1.1.1 TOY clock

rDThis is battery backed up hardware timing circuitry used to keep theAcorrect time of year during rebooting, power failures, and systemODshutdown. This clock only keeps track of months, days, and time. TheDtime is kept relative to January 1st, at 00:00:00.00 of the year theclock was initiailized.w

cEThe VAX Time-Of-Year (TOY) clock (used to save the time over a rebootdEor power failure) is specified as having an accuracy of 0.0025%. Thise+is a drift of roughly 65 seconds per month. 

FThe VAX Interval Time is used to keep the running time, and this has aAspecified accuracy of .01%. This is a drift of approximately 8.64wseconds per day.

/CAny high-IPL activity can interfere with the IPL 22 or IPL 24 (this Edepends on the VAX implementation) clock interrupts---activities suchaCas extensive device driver interrupts or memory errors are known tohslow the clock.t;

4.1.1.1.2 EXE$GQ_SYSTIME

/GThis is the OpenVMS VAX system time cell. This cell contains the numberoGof 100ns intervals since a known reference. This cell is incremented by 0100000 every 10ms by an hardware interval timer.9

4.1.1.1.3 EXE$GQ_TODCBASE

aFThis cell contains the time and date the system time was last adjusted=by EXE$SETTIME. It uses the same format as EXE$GQ_SYSTIME. OnCadjustment of the system time a copy of EXE$GQ_SYSTIME is stored indGthis cell in both memory and on disk. This cell is used to get the yearfor the system time.1

4.1.1.1.4 EXE$GL_TODR

2FThis cell contains the time and date the system time was last adjustedby EXE$SETTIME. GIt uses the same format as the time of year clock. On adjustment of thetBsystem time this cell gets saved back to both memory and disk. TheEcontents of this cell are used to test the validity of the TOY clock.r

lBThe system parameters SETTIME and TIMEPROMPTWAIT determine how thesystem time will be set.

    /
  • IF SETTIME = 0 and the TOY clock is validt
    ;THEN the contents of the TOY clock are compared to those ofCEXE$GL_TODR. IF the TOY clock is more than a day behind EXE$GL_TODRo
    'THEN the TOY clock is presumed invalid.5
      7
    • IF the TOY clock is within a day of EXE$GL_TODR 
      .THEN the system time is calculated as follows:G
    • EXE$GQ_SYSTIME = EXE$GQ_TODCBASE + ((TOY_CLOCK - EXE$GL_TODR) *D 100000)
    0
  • IF SETTIME = 1 or the TOY clock is invalid
    DTHEN the value of TIMEPROMPTWAIT determines how to reset the time ofyear. IF TIMEPROMPTWAIT > 0
    ETHEN the user is prompted for the time and date, for a length of timeg(equal to TIMEPROMPTWAIT microfortnights.
      
    • IF TIMEPROMPTWAIT = 0V
      9THEN the time of year is the value of EXE$GL_TODR + 10ms.
    • IF TIMEPROMPTWAIT < 0
      to proceed until they do so.B
    • THEN the user is prompted for the time and date and unable
    
5

GWhen booting a CD-ROM containing an OpenVMS VAX system, the system willhFtypically be deliberately configured prompt the user to input the time<-- this is necessary in order to boot with the correct time.

g4If either TIMEPROMPTWAIT or SETTIME are set to zero,HOpenVMS VAX will use the TOY clock to get the time of year, and the yearFwill be fetched from the distribution medium. The value of the year onBthe distribution medium (saved within the SYS.EXE image) will mostClikely be that of when the kit was mastered, and cannot be changed.eBUnless the current year happens to be the same year as that on theDdistribution, most likely the year will be incorrect. (Further, withFthe calculation of Leap Year also being dependent on the current year,Bthere is a possibility that the date could be incorrect, as well.)h

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FSupdate-request@goatley.com 1