Conference hydra::axp-developer

3336.0. "TIBCO" by AMCUCS::SWIERKOWSKI (Quot homines tot sententiae) Mon Mar 17 1997 21:09

    Company Name :  TIBCO
    Contact Name :  Taihsing Cha
    Phone        :  (415) 846-5067
    Fax          :  
    Email        :  "tcha@tibco.com"
    Date/Time in :  17-MAR-1997 17:44 
    Originally entered by :  SWIERKOWSKI
    SPE center   :  PAG

    Category     :  OpenVMS Alpha
    OS Version   :  V6.2
    System H/W   :  AlphaStation 400 4/233


    Brief Description of Problem:
    -----------------------------

  Called re: file access from a "C" program.  The program reads a file that is
written to by another process.  The second process only reads records present
in the file at the time it opens it and does not pick up new records subsequent-
ly written by the first process.

  I'm just guessing that he has got his "sharing" attributes wrong upon the
file open.  If this is OpenVMS/RMS, you tell RMS two things: the access you
want (i.e. Read-Only or Read/Write) and the access you want others to have.
By default, when you open a file (in most languages) the "SHR" bits are all
clear (i.e. no sharing with a subsequent process that tries to open the same
file).  A second process that comes along and tries to open the file already
opened by the first process is at best going to open a new version of the
file (which of course hasn't been written to).  The other possibility is to let
the second process cycle through an close/open cycle each time it wnts to pick
up the new EOF.  I'll research this and get back to him, cheers...




						Tony Swierkowski
						Digital Equipment Corporation
						Software Partner Engineering
						Palo Alto, California
						(415) 617-3601
						"swierkowski@pa.dec.com"

Greetings!

  I've starting researching this and I don't believe there is any inherent bug
in RMS that prevents file sharing in general and/or correctly updating the EOF
marker when the first process (which writes records) continues to do so after
the second process (which reads records) opens the file.  Having said that,
multiple notes here & there suggest that the application may have to cycle 
through a disconnect/connect sequence to pick up the updated EOF however.  I'm
not aware of a more "elegant" solution and I still have some questions about 
the DEC C RTL vs calling RMS Services directly.  I've crafted a message to 
Taihsing with some basic questions and await feedback...


						Tony Swierkowski
						Digital Equipment Corporation
						Software Partner Engineering
						Palo Alto, California
						(415) 617-3601
						"swierkowski@pa.dec.com"

Greetings!

  After more email tag back and forth with Tai-Hsing, he seems happy with the
solution I presented him with, call closed...


						Tony Swierkowski
						Digital Equipment Corporation
						Software Partner Engineering
						Palo Alto, California
						(415) 617-3601
						"swierkowski@pa.dec.com"