[Info-vax] OS implementation languages

[gah4]

On Sunday, September 3, 2023 at 5:16:44 AM UTC-7, Johnny Billquist wrote:

(snip)

> There is still some issues with ODS that certainly could be improved. 
> But then it's usually actually RMS that is the bottleneck. But as Bob 
> Gelzer observed and commented, RMS can be tweaked to at least give much 
> better performance that it does by default. 
 
(snip)

> I think I remember from maybe a year ago that RMS under VMS don't allow 
> you to us locate mode for writes. Which means that any writing of data 
> via RMS involves at least one data copy. That's sad, and it would be 
> nice if it was improved. RMS under RSX do allow locate mode for writes. 
 
> But I wonder how much code isn't using locate mode for reads as well, 
> meaning yet another copying of data there. 

IBM OS/360 and successors allow for locate mode I/O. 

Even PL/I allows for it.

But the OS/360 CKD disks allow a program to specify the size of each
physical block on the disk.  So, record boundaries also match up to
block boundaries.  (For files with variable length records and blocks,
they are written to that exact size by the hardware.)

Depending on the file system and blocking, though, it might be that record
boundaries don't match up.  That complicates locate mode I/O.