[Info-vax] Large mailboxes

[Arne Vajhøj]

On 11/27/2020 9:00 PM, Jan-Erik Söderholm wrote:
> Den 2020-11-27 kl. 23:41, skrev Arne Vajhøj:
>> On 11/26/2020 1:27 PM, Arne Vajhøj wrote:
>>> On 11/26/2020 11:30 AM, Marc Van Dyck wrote:
>>>> So my question is, why this limitation ? Is it just because when this
>>>> interface was written, noone imagined that there could ever be a
>>>> mailbox with more than 64k outstanding messages ? Or am I really going
>>>> to break something other than this counter if I try loading more
>>>> than 64k messages ?
>>>
>>> I don't know.
>>>
>>> But it seems likely that noone imagined it being a problem.
>>>
>>> It uses non-paged pool. How big was available non-paged pool on
>>> VAX systems?
>>>
>>> My guess is that available non-paged pool divided by a
>>> normal message size would fit into 16 bit.
>>
>> I could add that as a rule of thumb I would
>> only use VMS mailboxes (or Windows pipes or
>> *nix unix sockets) to buffer hundreds or a
>> few thousands of messages.
>>
>> If I needed hundreds of thousands or
>> millions I would look for a message queue
>> (and if I needed billions I would look at
>> Kafka).
> 
> Isn't the normal way to use a VMS mailbox as an on-line interface
> between one (or more) senders and one recevier? That is, the
> mailbox as such is never intended to "store" anything apart from
> a very short time during the transmission.
> 
> If the intention is to buffer 10000's or 100000's of messages,
> VMS mailboxes looks as the wrong tool from the toolbox...

Yes. That was sort of my point.

But if the writer is not blocking and the reader is
slower than the writer then some messages can queue up.

Arne