[Info-vax] VMS enhancement suggestion: Add a "read regardless" file open option.

[geze...@rlgsc.com]

On Tuesday, November 10, 2020 at 10:43:43 AM UTC-5, Chris Townley wrote:
> On 10/11/2020 16:21, VAX... at SendSpamHere.ORG wrote: 
> > In article <031830bf-747b-46db... at googlegroups.com>, Hein RMS van den Heuvel <heinvand... at gmail.com> writes: 
> >> On Monday, November 9, 2020 at 5:35:32 PM UTC-5, Tom Wade wrote: 
> >>> On 2020-11-09 13:30, Simon Clubley wrote:=20 
> >>>> On RSTS/E, you can view the contents of a file opened for write by=20 
> >>>> specifying mode 4096 as in:=20 
> >>>> =20 
> >>>> pip filename.dat/mo:4096=20 
> >>>> =20 
> >>>> What would be involved in adding a "read regardless" file open option= 
> >> =20 
> >>>> to VMS which would allow the opening of files for read only even if=20 
> >>>> they are already open for write, and then adding a qualifier to $ TYPE= 
> >> =20 
> >>>> to use this new option ? 
> >>> If you want to read files that are locked by another process, check out= 
> >> =20 
> >>> the Ralf utility at www.tomwade.eu/software=20 
> >>> =20 
> >>> Ralf is written as a callable utility, but has a command line PEEK=20 
> >>> [/page] program that displays a locked file. We used it extensively to=20 
> >>> examine PMDF message files that were being processed (and therefore locke= 
> >> d).=20 
> >>> =20 
> >>> =20 
> >>> Tom Wade=20 
> >>> tom dot wade at tomwade dot eu 
> >> 
> >> Well, it will only be partially useful as many such files write-no-share fi= 
> >> le are written by RMS or an RTL actively buffering data to be written in in= 
> >> complete chucks. 
> >> RMS by default could have an 8KB or 16 KB buffer only written when full. T= 
> >> he most recent record will only exist in process memory. RMS has a minor ba= 
> >> ckdoor to try an flush on exit, but I don't think there is a way to jiggle = 
> >> that conditions. So it could all be very disappointing. 
> >> 
> >> You can verify with BACK/IGNORE=3DINTERLOCK whether it would or would not s= 
> >> ufficiently solve a good part of the business needs. 
> >> I hope it is clear it will not at all be what folks expect and very hard to= 
> >> explain. 
> >> 
> >> To properly solve this and similar problem you really need a system buffer. 
> >> RMS/VMS engineering spend upwards of 2 manyears to define 'stream' file ac= 
> >> cess back in the 90ies but nothing practical transpired. 
> >> I believe most solution still ended up with the applications needing to 'do= 
> >> ' something, which is the very thing that we all want to avoid. 
> >> 
> >> As Brian says it may be easier hack the applications (Patch!) to initialize= 
> >> the fabs with sharing option and take the 'hit' of the locking overhead. 
> > 
> > ... or simply correct the application(s) writing the logs to have read share. 
> > 
> > Patching the application(s) would require locating the associated FAB which I 
> > would have little problem doing but others may. I could probably hack RMS to 
> > do it but I think I've done enough RMS hacking for more than one lifetime. ;) 
> >
> Woudln't it be possible to change the batch processor to make log files 
> readable? 
> 
> Chris
Chris,

Last time I checked, they were.  The frequency of writing can be reset using the SET OUTPUT_RATE command (default is one minute interval).

- Bob Gezelter, http://www.rlgsc.com