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

[Dave Froble]

On 5/29/2018 8:00 PM, Arne Vajhøj wrote:
> On 5/29/2018 7:53 PM, Johnny Billquist wrote:
>> On 2018-05-30 01:30, Arne Vajhøj wrote:
>>> On 5/29/2018 7:12 PM, Johnny Billquist wrote:
>>>> On 2018-05-29 01:16, Arne Vajhøj wrote:
>>>>> On 5/28/2018 4:08 PM, Johnny Billquist wrote:
>>>>>> Applications could be clever enough to actually refer to fields
>>>>>> based on names, instead of just using fixed, known, chunks of the
>>>>>> record. RMS do have names for the fields, which you can set and read.
>>>>>
>>>>> Both keys and values or only keys?
>>>>>
>>>>> I suspect key info is in XABKEY, but where do you find value info?
>>>>
>>>> What do you mean by value info? The values are in the individual
>>>> records obviously. And the key info will tell you which bytes in the
>>>> record that contains the value. Or are you talking about the type of
>>>> the value? Which also also stored with they key info.
>>>>
>>>> Not entirely sure what you are thinking of....
>>>
>>> If you have a record with 12 fields:
>>>
>>> Key_1
>>> Key_2
>>> Value_1
>>> ...
>>> Value_10
>>>
>>> then I assume that I can get the names, indexes and size for
>>> Key_1 and Key_2 from XABKEY (I have not tried it, but it looks
>>> promising), but I have no idea where I would get names, indexes
>>> and size for Value_1, ..., Value_10.
>>
>> I think we're talking past each other. A record is all values. The
>> keys are the names of the fields.
>> What you call "key_1" here is for me a value. (Or maybe I'm
>> misunderstanding you.)
>> However, as Hoff pointed out, fields that are not defined as keys do
>> not have this kind of meta information.
>>
>> So if you have fields which are not defined as keys, then you will not
>> have this information. I was in my mind looking at the case that you
>> have keys defined for all the fields.
>
> I see a record as consisting of fields and those fields can be
> either key fields or value fields.

All key data is just data.  There is no key data that isn't available 
for use.

> It is possible a RDBMS way of describing things.

Same thing with any RDBMS I'm aware of.  Keys are just data fields with 
some type of indexing to allow direct access.

> But it does match rather well how RMS index-sequential file
> access work in VMS Pascal.
>
> Example:
>
> type
>     string = varying [255] of char;
>     fixstring = packed array [1..8] of char;
>     isqrec = record
>                 keyfield  : [KEY(0)] fixstring;
>                 bodyfield : string;
>              end;
>
> But I think we got it sorted out.
>
> Arne
>