| Previous | \Contents | ^Index |
C Some of the OpenVMS books that are or have been available from the Digital Press imprint
G are listed in Table 3-4:
| Title and Author | ISBN |
|---|---|
| 4 Getting Started with OpenVMS System Management David Donald Miller | 1-55558-281-8 |
| * 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 |
F For various featured OpenVMS books, also please see the books link at the OpenVMS website:
8 For a bibliography of various OpenVMS books, please see:
d¨ Various OpenVMS mailing lists are available, with some of the available lists detailed in Table 3-5.
| 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 |
| - The SRI CHARON-VAX VAX emulator package | " 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.edu 1 |
| ? RADIUS-VMS, a RADIUS server for OpenVMS discussion forum | radius-vms@dls.net% radius-vms-request@dls.net 1 |
| 7 Internet Service Providers (ISPs) running OpenVMS | vms-isps@dls.net# vms-isps-request@dls.net 1 |
| G Users of Mark Daniel's WASD web server for OpenVMS VAX and Alpha G exists. Information about this list server and details on how to D subscribe to the list are available at the referenced website. | @ http://wasd.vsm.com.au/ |
| VMS Forum | H < http://www.neurophys.wisc.edu/comp/ava/vms_forum.htmlx |
# The HP OpenVMS Ask The Wizard (ATW) G website is an informal area containing questions and answers on a wide variety of topics.
H For additional information on the OpenVMS Ask The Wizard (ATW) area and B for a pointer to the available ATW Wizard.zip archive, please see 0 Section 3.9.
7 To access a cited topic directly, use the URL filename A WIZ_topic-number.HTML. For example, topic (1020) can be accessed C directly using the URL filename wiz_1020.html at the following URL:
H A zip archive (named wizard.zip) containing all of the available topics B and questions can be downloaded from the above URL. The wizard.zip F zip archive is completely regenerated when new batches of topics are posted out to the ATW website.
F Before posting a question to the Ask The Wizard area, please read and C please heed the posting rules---and please remember to search this G document, the OpenVMS FAQ. And if you have a question that requires an F answer, or if your question has time-critical constraints or business D constraints, please contact the HP customer support center directly. s 3.10 Access to the OpenVMS Netscape Navigator documentation?
H The documentation URLs embedded into the browser itself may not operate G correctly in all cases, and (for reasons not worthy of repeating here) redirects may not be available.
. You can manually access the documentation via:
h For information on the Mozilla web browser, please see Section 13.4. u 3.11 Where can I find the latest C run-time library manuals?
D The C run-time library (RTL) reference documentation has been moved H from the C language documentation set to the OpenVMS documentation set. G For the most recent version of the C RTL documentation and the OpenVMS 3 standard C library, please see the OpenVMS manuals.
F In addition to the user-mode C RTL, there is a second kernel-mode RTL G accessable to drivers on OpenVMS Alpha and OpenVMS I64. For details on C this second library and on the duplicate symbol errors that can be 4 triggered when this library is referenced during an j incorrectly-specified LINK command, please see Section 10.22.1. For C general information on this kernel RTL, see the Digital Press book A Writing OpenVMS Device Drivers in C. For details, please see the 0 associated OpenVMS source listings distribution.
G This chapter discusses time, timekeeping, system time synchronization, 2 clock skew and clock drift, implications of using 5 SUBMIT/AFTER=TOMORROW, and other time-related topics. j 4.1 A brief history of OpenVMS Timekeeping, please?
F Why does OpenVMS regards November 17, 1858 as the beginning of time...
B The modified Julian date adopted by the Smithsonian Astrophysical Observatory (SAO) / for satellite tracking is Julian Day 2400000.5, 4 which turns out to be midnight on November 17, 1858.
G SAO started tracking satellites with an 8K (nonvirtual) 36-bit IBM 704 D in 1957 when Sputnik went into orbit. The Julian day was 2435839 on G January 1, 1957. This is 11225377 octal, which was too big to fit into B an 18-bit field. With only 8K of memory, the 14 bits left over by G keeping the Julian date in its own 36-bit word would have been wasted. H SAO also needed the fraction of the current day (for which 18 bits gave F enough accuracy), so it was decided to keep the number of days in the H left 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) to E grow as large as 262143, which from November 17, 1858, allowed for 7 H centuries. Possibly, the date could only grow as large as 131071 (using G 17 bits), but this still covers 3 centuries and leaves the possibility F of representing negative time. The 1858 date preceded the oldest star H catalogue in use at SAO, which also avoided having to use negative time . in any of the satellite tracking calculations.
E The original Julian Day (JD) is used by astronomers and expressed in > days since noon January 1, 4713 B.C. This measure of time was A introduced 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 calendar 4 that is named for the Roman Emperor Julius Caesar!).
H Why 4713 BC? Scaliger traced three time cycles and found that they were F all in the first year of their cyle in 4713 B.C. The three cycles are G 15, 19, and 28 years long. By multiplying these three numbers (15 * 19 G * 28 = 7980), he was able to represent any date from 4713 B.C. through 3267 A.D.
C The starting year was before any historical event known to him. In D fact, the Jewish calendar marks the start of the world as 3761 B.C. E Today his numbering scheme is still used by astronomers to avoid the D difficulties of converting the months of different calendars in use during different eras.
The following web sites:
G are all good time-related resources, some general and some specific to OpenVMS. O 4.1.1 Details of the OpenVMS system time-keeping?
R 4.1.1.1 VAX hardware time-keeping details...
3 4.1.1.1.1 TOY clock
E This is battery backed up hardware timing circuitry used to keep the B correct time of year during rebooting, power failures, and system E shutdown. This clock only keeps track of months, days, and time. The E time is kept relative to January 1st, at 00:00:00.00 of the year the clock was initiailized. ; 4.1.1.1.2 EXE$GQ_SYSTIME
H This is the OpenVMS VAX system time cell. This cell contains the number H of 100ns intervals since a known reference. This cell is incremented by 0 100000 every 10ms by an hardware interval timer. 9 4.1.1.1.3 EXE$GQ_TODCBASE
G This cell contains the time and date the system time was last adjusted > by EXE$SETTIME. It uses the same format as EXE$GQ_SYSTIME. On D adjustment of the system time a copy of EXE$GQ_SYSTIME is stored in H this cell in both memory and on disk. This cell is used to get the year for the system time. 1 4.1.1.1.4 EXE$GL_TODR
G This cell contains the time and date the system time was last adjusted by EXE$SETTIME. H It uses the same format as the time of year clock. On adjustment of the C system time this cell gets saved back to both memory and disk. The E contents of this cell are used to test the validity of the TOY clock.
C The system parameters SETTIME and TIMEPROMPTWAIT determine how the system time will be set.
H When booting a CD-ROM containing an OpenVMS VAX system, the system will G typically be deliberately configured prompt the user to input the time < -- this is necessary in order to boot with the correct time.
4 If either TIMEPROMPTWAIT or SETTIME are set to zero, H OpenVMS VAX will use the TOY clock to get the time of year, and the year G will be fetched from the distribution medium. The value of the year on C the distribution medium (saved within the SYS.EXE image) will most D likely be that of when the kit was mastered, and cannot be changed. C Unless the current year happens to be the same year as that on the E distribution, most likely the year will be incorrect. (Further, with G the calculation of Leap Year also being dependent on the current year, B there is a possibility that the date could be incorrect, as well.) S 4.1.1.2 Alpha hardware time-keeping details...
N 4.1.1.2.1 Battery-Backed Watch (BB_WATCH) Chip
E This is battery backed up hardware timing circuitry used to keep the B correct time of year during rebooting, power failures, and system D shutdown. This clock keeps track of date and time in 24 hour binary format.
G The BB_WATCH time is used to initialize the running system time during F bootstrap, and the BB_WATCH time is read when the SET TIME command is H issued with no parameters; when the running system time is reset to the F value stored in the BB_WATCH. The running system time is written into B the BB_WATCH when the SET TIME command is issued with a parameter. = 4.1.1.2.2 EXE$GQ_SYSTIME
C This is the OpenVMS Alpha system time cell. This cell contains the D number of 100ns intervals since November 17, 1858 00:00:00.00. This G cell is incremented by 100000 every 10ms by an hardware interval timer. = 4.1.1.2.3 EXE$GQ_SAVED_HWCLOCK
F This cell is used by OpenVMS Alpha to keep track of the last time and H date that EXE$GQ_SYSTIME was adjusted. It keeps the same time format as E EXE$GQ_SYSTIME. The value in this cell gets updated in memory and on . disk, every time EXE$GQ_SYSTIME gets adjusted.
H Unlike the VAX, the Alpha hardware clock tracks the full date and time, F not just the time of year. This means it is possible to boot from the F CD-ROM media without entering the time at the CD-ROM bootstrap. (This B provided that the time and date have been initialized, of course.)
< IA-64 (Itanium) hardware time-keeping details to be added... W 4.1.1.3 Why does VAX need a SET TIME at least once a year?
E Because the VAX Time Of Year (TOY) has a resolution of 497 days, the H VAX system time is stored using both the TOY and the OpenVMS VAX system D image SYS.EXE. Because of the use of the combination of the TOY and G SYS.EXE, you need to issue a SET TIME command (with the time parameter E specified) at least once between January 1st and about April 11th of A each year, and whenever you change system images (due to booting H another OpenVMS VAX system, booting the standalone BACKUP image, an ECO that replaces SYS.EXE, etc).
? The SET TIME command (with the current time as a parameter) is H automatically issued during various standard OpenVMS procedures such as E SHUTDOWN, and it can also obviously be issued directly by a suitably H privileged user. Issuing the SET TIME command (with a parameter) resets A the value stored in the TOY, and (if necessary) also updates the C portion of the time (the current year) saved in the SYS.EXE system image.
G This VAX TOY limit is the reason why OpenVMS VAX installation kits and G standalone BACKUP explicitly prompt for the time during bootstrap, and E why the time value can "get weird" if the system crashes outside the G 497 day window (if no SET TIME was issued to update the saved values), 6 and why the time value can "get weird" if a different F SYS$SYSTEM:SYS.EXE is used (alternate system disk, standalone BACKUP, etc). M 4.1.2 How does OpenVMS VAX maintain system time?
= VAX systems maintain an interval clock, and a hardware clock.
E The VAX hardware clock is called the TOY ("Time Of Year") clock. The D register associated with the clock is called the TODR ("Time Of Day Register").
G The TOY clock---as used---stores time relative to January first of the A current year, starting at at 00:00:00.00. It is a 100 Hz, 32-bit F counter, incremented every 10ms, and thus has a capacity of circa 497 days.
F OpenVMS (on the VAX platform) stores system date information---and in G particular, the current year---in the system image, SYS$SYSTEM:SYS.EXE.
F The TOY is used, in conjunction with the base date that is stored and H retrieved from the system image, to initialize the interval clock value ! that is stored in EXE$GQ_SYSTIME.
E Once the interval clock is loaded into the running system as part of F the system bootstrap, the system does not typically reference the TOY again, unless a F SET TIME (with no parameters) is issued. The interval clock value is A updated by a periodic IPL22 or IPL24 (depending on the specific D implementation) interrupt. (When these interrupts are blocked as a F result of the activity of higher-IPL code---such as extensive driver G interrupt activity or a hardware error or a correctable (soft) memory C error---the clock will "loose" time, and the time value 7 reported to the user with appear to have slowed down.)
D When SET TIME is issued with no parameters, the TOY clock is loaded C into the system clock; the running system clock is set to the time E stored in the TOY clock. This assumes the TOY clock is more accurate / than the system clock, as is normally the case.
H On most (all?) VAX systems, the battery that is associated with the TOY F clock can be disconnected and replaced if (when) it fails---TOY clock H failures are quite commonly caused by a failed nickel-cadmium (NiCd) or , lithium battery, or by a failed Dallas chip. h 4.2 Keeping the OpenVMS system time synchronized?
E To help keep more accurate system time or to keep your system clocks H synchronized, TCP/IP Services NTP, DECnet-Plus DTSS (sometimes known as E DECdtss), DCE DTS, and other techniques are commonly used. If you do G not or cannot have IP access to one of the available time-base servers D on the Internet, then you could use dial-up access to NIST or other B authoritative site, or you can use a direct connection to a local authorative clock.
H There exists code around that processes the digital (ie: binary) format A time that is available via a modem call into the NIST clock (the > Automated Computer Telephone Service (ACTS) service), and code C that grabs the time off a GPS receiver digital link, or a receiver G (effectively a radio and a codec) that processes the time signals from + radio stations WWV, WWVH, WWVB, or similar.
G Processing the serial or hardware time protocols often involves little H more than reading from an EIA232 (RS232) serial line from the receiver, B something that is possible from most any language. Information on H correctly drifting the OpenVMS system clock to match the time-base time G is available within the logic of at least one OpenVMS Freeware package.
F One example of acquring a time-base through local integrated hardware involves the IRIG time format H (IRIG-A, -B, -G), a binary signal containing the current time in hours, H minutes, seconds and days since the start of the current year. IRIG can F also contain the time of day as the number of seconds since midnight. A HP Custom Systems and third-party vendors have variously offered 8 IRIG-based reader/generator modules for OpenVMS systems.
F One of the easiest approaches is a network-based GPS or other similar G receiver. Basically, this is a network server box that provides an NTP D server with the necessary hardware for external synchronization. In D addition to the antenna and the receiver and processing components, G these devices provide a network interface (NIC) and support for an NTP F time server, and applications including the NTP support within TCP/IP F Services and within various third-party IP stacks can then be used to ? synchronize with the the NTP information provided by time-base ; receivers. No other host software is required, and no host A configuration steps and no host software beyond NTP are required.
C Differing time servers (DECnet-Plus DTSS, DCE DTS, NTP, etc) do not D coexist particularly well, particularly if you try to use all these E together on the same node. Please pick and use just one. (If needed, E you can sometimes configure one package to acquire its timebase from G another protocol, but one and only one time server package should have H direct control over the management of and drifting of the local OpenVMS E system time. In the specific case of DECnet-Plus DTSS, older product B versions and versions V7.3 and later provide a provider module, a G module which permits DTSS to acquire its time from NTP. For details on A this, please see the comments in the module DTSS$NTP_PROVIDER.C.)
H Unlike DECnet-Plus, TCP/IP Services NTP is not capable of connecting to H a time-base other than the network time base or the local system clock. B Third-party and open source NTP implementations are available for OpenVMS, as well.
Useful URLs:
| Previous | YNext | \Contents | ^Index |