[Info-vax] The best VMS features, was: Re: openvms renaming file

[Arne Vajhøj]

On 5/28/2018 4:42 PM, Craig A. Berry wrote:
> On 5/28/18 2:58 PM, Arne Vajhøj wrote:
>> On 5/28/2018 3:17 PM, seasoned_geek wrote:
>>> On Monday, May 28, 2018 at 1:31:49 PM UTC-5, Arne Vajhøj wrote:
>>>> On 5/28/2018 11:01 AM, Dave Froble wrote:
>>>>>>
>>>>>> But maybe great for replacing index-sequential files.
>>>>>
>>>>> I don't think so.  RMS indexed files allow concurrent use, using 
>>>>> the DLM.
>>>>
>>>> You are right.
>>>>
>>>> SQLite will only replace let us say the low-end of index-sequential
>>>> files usage.
>>>
>>> That is making the grand assumption that SQLite on VMS wouldn't 
>>> integrate
>>> DLM support.
>>
>> That would be a major rewrite of SQLite. Not realistic.
> 
> Have a look at the port here:
> 
> <https://sourceforge.net/projects/vms-ports/files/SQLITE3/>
> 
> In particular note the file called "sqlite3_prv_lock.dcl" the header of
> which starts with:
> 
> $!                            1.5, 30-SEP-2015
> $! Build the sqlite_prv_lock proteced shareable image to support 
> implementing
> $! the SQLITE3 database locking model with distributed lock manager locks.
> $! The protected image provides exec mode system services to create system
> $! locks associated with files open by the caller via SYS$OPEN().
> $!
> 
> I have not delved deeply enough to see if it provides more granular
> locking than is available on other platforms, but it does provide an
> option to use the DLM.

If:
* SQLite already has isolated all lock functionality out in
   a separate module
* SQLite will work with shared file access if the lock module
   works across processes
* the lock functionality can be implemented via VMS lock
   manager
then it should be relative easy.

Does anyone know if this is actually the case?

Arne