[Info-vax] OpenVMS async I/O, fast vs. slow

[Craig A. Berry]

On 11/3/23 11:08 AM, David Jones wrote:
> On Friday, November 3, 2023 at 10:08:11 AM UTC-4, Arne Vajhøj wrote:
>> I have never seen VMS code dynamic allocate an IOSB in heap - either
>> stack or static heap.

The alternative being what?  A finite pool of global buffers?

> For network code, it was pretty common for me to allocate from the heap
> composite structures that included both a buffer and IOSB since the number
> of pending I/O requests depended upon the number of concurrent client
> connections.

And moreover, an IOSB on the stack is kind of a non-starter for
asynchronous code since it will very likely have gone out of scope
before the completion routine needs to check its contents. It's
completely normal and convenient, though, (and quite common) if you're
calling the versions of system services that end it "w."