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

[Chris Townley]

On 10/11/2020 16:21, VAXman- at SendSpamHere.ORG wrote:
> In article <031830bf-747b-46db-8887-1eb00b0b840en at googlegroups.com>, Hein RMS van den Heuvel <heinvandenheuvel 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