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**** The Hebrew University of Jerusalem ****
**** Computation Center ****
News Bulletin #14
18-November-1990
Today's topics:
- Tape labels and using BACKUP command.
- New tape media available on the VAX for backup storage.
- Old files expiration dates.
- BMAIL's new command: VERIFY.
- Internet libraries.
- Telnet 3270.
- Printers and files' carriage control.
o Tape labels: When you write a tape using BACKUP and a second tape
is needed, BACKUP tries to compute the number of the next tape by
its own. It takes the first tape label and replaces the last two
characters of it with the serial number (in this BACKUP operation)
of the next tape. For example, if you started writing on a tape
whose label is PR1567 (and we assume that you use the same label as
the external VSN of the tape), when BACKUP needs a second tape it'll
ask for a tape labeled PR1502 (and for the third PR1503 and so on).
This is bad since there is a tape named PR1502 which is probably not
the intended one...
The solution is to inform BACKUP what label it should use for the
second tape. If you suspect that your job will need more than one
tape use the /LABEL qualifier of BACKUP:
$ BACKUP/LABEL=(first-tape-label,second-tape-label,...) ...
For example, if we suspect that our BACKUP job will need 3 tapes,
and we want to use tapes PR1667, PR1690, PR1610 (in that order), the
BACKUP command will look like:
$ BACKUP/LABEL=(PR1667,PR1690,PR1610) ...
Note: It is suggested that you'll use as label the external VSN of
the tape. This is the only way to enable usage of such continuation
tape's labeling.
Tape densities: When you intialize a tape the drive uses the lowest
density available (1600 bpi in our case); if the tape was used
already it will use the existing tape's density. Since most drives
today accept the higher density tapes you can force INIT to use the
higher density with the qualifier /DENSITY=6250 (which should be
used on BACKUP also if you are writing a tape). If you have to take
the tape to a different institute and need the lower density use the
qualifier /DENSITY=1600.
When using the higher density BACKUP's default block size (8192
bytes) wastes a large amount of tape length. If you are using
BACKUP to write a tape at the higher density add the qualifier (only
when writing the tape!) /BLOCK=32256 which will create blocks of
32256 bytes on the tape. To summarize, if you want to write high
density tapes use the command:
$ BACKUP/DENSITY=6250/BLOCK=32256...
For more details consult the guide TAPES.
o New tape media available: One of the tape drives used on the VAX
uses tape cartridges which are known as TA90 (or more known with the
IBM name of 3480). These cassetes are faster than tapes, hold more
data (up to 200 Mb per cartridge), smaller and sometimes cheaper.
The main disadvantages are that there are only few sites who use
these cassetes on VAX systems and that you have to buy them in large
quantities. Hence, these cartridges are recommended to those who
have to store large amount of data for use on the local system.
o Old files expiration date: The policy of the computation center is
to remove files which are not touched for two months. As you
probably noted this is not done. However, when disk space becomes
scarce we'll start activating this files' removal without prior
notice.
o BMAIL's VERIFY command: A new command was added to BMAIL which
verifies its internal databases integrity. When you hit the VERIFY
command it'll scan your bmail's directory for files which are not
entered in any folder. Such files are entered into the NEWMAIL
folder. Entries in folders which have no files associated with them
are deleted. Due to bugs in old versions of BMAIL you might have a
few files which are inaccessible now; this command will remove their
incorrect entry and enter them into the NEWMAIL folder.
It is recommended to use this command once in a few weeks.
o InterNet libraries: As was said in previous bulletins, there are a
lot of libraries which are accessible via the InterNet. An updated
copy of the guide INTERNET.LIBRARY has been replaced in GUIDES$
directory.
o TN3270 - IBM systems are peculiar in the way that ASCII terminals
(and thus also TELNET connections) are handled. IBM's own terminals
are connected to a special controller which does all the screen
management work. When you want to use a simple ASCII terminal you
have to connect it to a special controller (named 7171) which does
all this work. However, when you Telnet to an IBM system you don't
have any such controller in the way. What you end with is a "line
mode" connection which is quite impossible to work with. The
solution is to do all the screen management on the local system (the
one which originated the Telnet connection) and this is called "3270
mode" in telnet. The local telnet here finds out automatically when
the other side is an IBM system and enters this mode transparently
to you. Now you have a problem: How the function codes are mapped?
A special file has been created to map the functions keys of most of
the terminals used at the university to be like the ones the 7171
controller is using. This means that on a VT100 compatible
terminals you have the following mapping of the keypad:
Eypad's PF1, PF2, PF3 are mapped to F1, F2, F3 (i.e. the same)
Keypad 7, 8, 9 are mapped to F4, F5, F6.
Keypad 4, 5, 6 are mapped to F7, F8, F9.
Keypad 1, 2, 3 are mapped to F10, F11, F12.
Keypad's key is the CLEAR one.
Note that your terminal must be in 7-bits control mode (not 7 bits
characters, only control mode). However, there are terminals on
which the mapping is incorrect. In these cases Telnet has a default
mapping of the functions which works always on all terminals:
Control/Z is the Clear function.
Hitting the key and then a number generates the function of
that number (ofcourse function 10 to 12 are not available here).
When you initiate a Telnet connection to an IBM system do not hit
any key untill you see the first screen. If you hit something
before you might enter line mode. When Telnet finds that it has to
use TN3270 mode it changes the escape character from Shift/Control/^
to Control/C.
o Printers and carriage control - When you have printed files on the
NOS (and similarly on the IBM) you had the options to print the
files "shifted" or "unshifted". In the first case the printer
accepted the first character of each line as a printer control
character, and in the second case it printed the first character
like the others. On the VAX there is no such notion of "shift" and
"noshift". The printer interprets or not the first character
according to a specific file attribute called "record attribute".
If this attribute (as seen in DIR/FULL command) is "carriage return"
then the file is printed single spaced (like the "shifted" mode on
the CDC). If this attribute is "Fortran carriage control" then the
first character is interpreted as printer control one, and there is
no way to force the printer to ignore it; the only way is to use
CONVERT and create a new file with different attributes. Files in
this format are usually created by Fortran programs.
If your program is written in Fortran and you want to disable this
behavior (print the first character as-is) then add to the OPEN
command the following field:
OPEN(UNIT=n, ..., CARRIAGECONTROL='LIST' ...)
Note the single qutation marks which are needed.
__Yehavi:
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