[Info-vax] VSI strategy for OpenVMS

[Arne Vajhøj]

On 9/16/2021 8:04 PM, Dave Froble wrote:
> On 9/16/2021 7:42 PM, Arne Vajhøj wrote:
>> On 9/16/2021 5:10 PM, Dave Froble wrote:
>>> On 9/16/2021 2:45 PM, Arne Vajhøj wrote:
>>>> On 9/15/2021 1:00 AM, Phillip Helbig (undress to reply) wrote:
>>>>> In article <shr7f4$tnu$1 at gioia.aioe.org>, =?UTF-8?Q?Arne_Vajh=c3=b8j?=
>>>>>> Let us take Rdb vs Oracle DB aka Classic with RAC (real RAC
>>>>>> not RAC One). Both use a DLM but Rdb use VMS DLM while Oracle DB
>>>>>> RAC use its own DLM.
>>>>>>
>>>>>> Does it matter for developers or operations? Not really.
>>>>>
>>>>> Have you ever worked anywhere where one tried to emulate the
>>>>> functionality of VMS with regard to clustering, availability, and 
>>>>> so on
>>>>> with non-VMS hardware and software?
>>>>
>>>> It was a very specific example where the same functionality is provided
>>>> by either DLM in the application or in the OS.
>>>>
>>>> I don't see why it would require more people to manage when
>>>> it is in the application.
>>>
>>> If it's in the application, who puts it there and maintains it?
>>>
>>> If it's in the OS, the required people for maintenance is zero.
>>
>> I cannot follow you.
>>
>> If we look at the stacks:
>>
>>                           Rdb        Oracle RAC
>> business application      X          X
>> RDBMS                     Oracle     Oracle
>> DLM                       VSI        Oracle
>> OS                        VSI        whoever
>>
>> The difference is that some work get moved from OS vendor to Oracle.
>>
>> But Oracle is probably not unhappy about that, because the
>> cost of maintaining the DLM is offset by the savings from
>> having the same DLM API across OS'es.
> 
> Ok, you're right to some extent, since the thread mentioned Rdb and Oracle.
> 
> But how about in-house custom developed applications?
> 
> Either one can use what's available, or, one must implement the locking 
> in the application.

It would be crazy for a business application to develop its
own DLM. It would be unnecessary work.

But it could make sense for a business application to
get an external library with DLM functionality.

It is not more difficult to call such a library than
the OS DLM (for VMS DLM it may even be easier as SYS$ENQW
is not that user friendly).

And if the business application are intended to be
available on multiple platforms and the DLM library
are also available on those platforms then it is a
huge benefit.

On the other side if the business application is
tied to a platform for other reasons and that platform
has a DLM, then there is no reason to look for an
external DLM library.

So it depends.

Arne