[Info-vax] CRTL and RMS vs SSIO

[Dave Froble]

On 10/6/2021 8:40 AM, Craig A. Berry wrote:
>
> On 10/5/21 9:06 PM, Greg Tinkler wrote:
>
>> An extra that could be added, if the file is RFM=fixed, and the C
>> code  uses it that way with the same record length then use the
>> SYS$GET/SYS$PUT so it will play nicely with an RMS access to those files.
>
> I don't know the degree to which the current plan corresponds to the
> original plan from a decade or so ago, but back then only stream files
> were going to be supported by SSIO, which makes sense since the whole
> point is locking byte ranges.

It has been my impression that for quite some time at HP, work on 
specific requests tended to be very specific to that request, and failed 
to consider capabilities as general to VMS.

The approach to SSIO appears to be an example of this.  Basically, do 
the least required to achieve the specific result.  In the case of SSIO 
the result appears to be rather useless, at least so far.

For some years I've advocated a more general enhancement to the VMS DLM, 
specifically, numeric range locking.  Such would address a basic issue 
I've had with the VMS DLM for a rather long time.

I've a database product, a rather old product.  At the time it was 
implemented it was rather useful.  But there was a locking issue.  The 
DLM locks resource names.  The database would support I/O transfers of 1 
to 127 disk blocks.  How would one lock 127 contiguous disk blocks?  The 
blunt force method could be taking out 127 locks, not an optimum 
solution.  Having numeric range locking back in 1984 would have been 
quite useful.

I've also suggested in the past that a simple enhancement to the DLM, 
specifically the addition of a "type of lock" with the capability of 
adding logic for specific "types" would solve the locking part of SSIO 
and do so as a part of VMS, not as part of the CRTL.

As for byte range I/O, I'm not sure what is and isn't possible with disk 
drives.  It has been my impression that only whole block transfers are 
possible.  Perhaps I've been wrong.  Perhaps SSDs have more flexibility.

Not really an issue for me anymore.

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