[Info-vax] Large mailboxes

[Dave Froble]

On 12/2/2020 4:40 PM, Jan-Erik Söderholm wrote:
> Den 2020-12-02 kl. 22:26, skrev Dave Froble:
>> On 12/2/2020 12:38 PM, Michael Moroney wrote:
>>> =?UTF-8?Q?Jan-Erik_S=c3=b6derholm?= <jan-erik.soderholm at telia.com>
>>> writes:
>>>
>>>> Den 2020-12-01 kl. 21:02, skrev Michael Moroney:
>>>>> So in theory, is it possible to implement a VMS file as a FIFO and
>>>>> work
>>>>> efficiently?  That is one process can write records in order, a second
>>>>> process can read and delete records in order, without RMS cruft from
>>>>> accumulating?
>>>>>
>>>
>>>> It depends on the definition of a "VMS file". I see no issues with
>>>> having
>>>> an Rdb table as the buffer.
>>>
>>> I kind of meant RMS file, something accessed via RMS
>>> $GET/$PUT/$DELETE or their
>>> high level equivalents.  I know if just disk space anything could be
>>> used.
>>>
>>>> Is there an indication on what "a fairly large number" of messages is?
>>>
>>> Maybe 6000 messages/day, it could vary quite a bit.
>>>
>>
>> I believe I mentioned linked lists earlier.
>>
>> If you desire to use an RMS file, a relative file could easily be used
>> for a linked list.  Multiple ways to design it.  One might be a file
>> with say 10,000 records, where part of the data is a link to the next
>> record in the list.  Could have reverse links also.  Have two lists, a
>> list of unused records, and a list of records with active messages.
>> Use simple logic to pop the next available unused record for use, and
>> to add a used record back to the list.  Front or back should not
>> matter. Always add new messages at the end of the list of messages.
>>
>> Really simple, really quick, no cruft, ....
>>
>> Considerations:
>>
>> If the list needs to be persistent, use record 1 for the list
>> pointers. Otherwise keep the pointers in memory.
>>
>> No reason there cannot be more than one message list.
>>
>
> Still much more application logic than a simple SQL INSERT... from one
> application and SQL SELECT..., <process>, SQL DELETE... from the other.
>
>

Jan-Erik

Did you ever hear the story about the devil's demo system?

Yes, what you mention can work.  I'm not too sure about it's 
performance.  I know, we don't worry about performance with today's 
hardware.  But still, 100 is always going to be more than 10.`

If there needs to be some logic involved in managing the list, then some 
programing will be required to impose that logic, thus applications 
could not go straight to the database.

Not every system will have a RDBMS available.  Sometimes that will be a 
consideration.

-- 
David Froble                       Tel: 724-529-0450
Dave Froble Enterprises, Inc.      E-Mail: davef at tsoft-inc.com
DFE Ultralights, Inc.
170 Grimplin Road
Vanderbilt, PA  15486