[Info-vax] CRTL and RMS vs SSIO

[Dave Froble]

On 10/7/2021 8:59 AM, Simon Clubley wrote:
> On 2021-10-07, Greg Tinkler <tinklerg at gmail.com> wrote:
>> On Thursday, 7 October 2021 at 11:26:38 pm UTC+11, Simon Clubley wrote:
>>
>>> How do you find byte 12,335,456 in a variable length RMS sequential file
>>> without reading from the start of the file ?
>>>
>>> That's why there are restrictions on RMS supported file formats in an
>>> application in some cases.
>>
>> The same way it is done on Unix, calculate the block offset, go get it, and extract the byte.  no difference and nothing to do with the underlying format.
>>
>
> You don't know the block offset without scanning the file when it comes
> to some RMS file formats.
>
> IOW, data byte 12,335,456 will not be the same thing as file byte 12,335,456
> unless you restrict yourself to record formats that do not have embedded
> record metadata.
>
> Simon.
>

I'm guessing Unix files don't have metadata and such.  So the comparison 
is not valid.

For a non-RMS file, yes, the location can be calculated.  But not so for 
an RMs file with record characteristics included in the records.

Since Unix doesn't have RMS files, perhaps that confused Greg.

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