[Info-vax] VMS enhancement suggestion: Add a "read regardless" file open option.
Chris Townley
news at cct-net.co.uk
Tue Nov 10 11:14:40 EST 2020
On 10/11/2020 15:54, geze... at rlgsc.com wrote:
> 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
>
So why cannot EDT read it?
Chris
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