[Info-vax] Ken Coar's OpenVMS Lock utility sources are available on Sourceforge.

[Simon Clubley]

On 2020-11-09, Stephen Hoffman <seaohveh at hoffmanlabs.invalid> wrote:
> On 2020-11-09 13:14:22 +0000, Simon Clubley said:
>
>> ...but the ability to use the DLM to notify everyone else that some 
>> activity or program is running is a far better approach than having to 
>> use lock files to indicate that.
>
> You're asking for a job scheduler.
>

No, I'm not.

Imagine if, for example, a webserver took out a lock at startup so you
know it's running. Or if a program took out a lock during a critical
section so that another instance of the program can't run the same
critical section at the same time.

If the web server (for example) crashes, the lock disappears without any
manual cleanup of a lock file required. Same if the system crashes
or there's a power failure.

> DLM might well be part of that scheduler implementation. But as an 
> interprocess notification and coordination mechanism, the DLM API... 
> does not deal easily with the common cases.
>

I can imagine a large number of common cases it deals with, including
the examples above.

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.