[Info-vax] CRTL and RMS vs SSIO

[Dave Froble]

On 10/8/2021 2:19 PM, Simon Clubley wrote:
> On 2021-10-07, Dave Froble <davef at tsoft-inc.com> wrote:
>>
>> Now I''m just a dumb polock, wandered down out of the woods.  But I just
>> don't see where upward compatibility has anything to do with
>> enhancements to the DLM.  If existing calls continue to work as before,
>> and only when an optional extra parameter would enable new capabilities,
>> then upward compatibility just cannot be an issue.  At least for this.
>>
>
> Is there a version number on the current inter-node DLM messages ?

Good question, and if not, perhaps such could be implemented.  However, 
what I envision should not affect usage of the existing resource name lock.

> If not, how can you change the DLM message structure in a compatible way ?
>
> If yes, what happens when an older node sees a later format DLM message ?
> You would at least need a compatibility kit to be installed on the older
> nodes.

Perhaps.

>> The optional parameter might be a "lock type", and if not present,
>> existing logic would be used, and if present, new code could be executed
>> to process the new lock type.  Stuff a couple of quadwords into the
>> resource name for the numeric range.  It would add one new piece of data
>> to the DLM data structure(s).
>>
>
> What about the DLM messages sent between nodes ?
>
> Simon.
>

First, re-read what I posted.  Specifically "if not present, existing 
logic would be used".

Not sure what you're calling "DLM message".

The only data item I'd see added to the lock database would be the "lock 
type", and that could be done in a manner such that it does not affect 
lock database information that does not  have the new structure definitions.

Perhaps it could be arranged that when using the new data structure(s), 
that it would be mandatory to update all nodes in a cluster.  Perhaps 
some type of version would disallow usage of dissimilar versions.

Note that any node or cluster that wished to use numeric range locking 
would have to have the enhancement installed.  If not using it, then 
nothing changes.

This could be done as a VMS DLM enhancement.  I'm rather sure of that. 
Whether the desire to do so might be a different issue.

-- 
David Froble                       Tel: 724-529-0450
Dave Froble Enterprises, Inc.      E-Mail: davef at tsoft-inc.com
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