[Info-vax] CRTL and RMS vs SSIO

[Stephen Hoffman]

On 2021-10-10 00:26:46 +0000, Lawrence D’Oliveiro said:

> I don’t think it has been traditional on *nix systems to bother with 
> much (if any) locking at all, at least not at the file I/O level. There 
> has never been anything on such systems (that I have seen) like the VMS 
> Lock Manager, distributed or otherwise. Any more elaborate locking 
> protocol needed would be implemented through the subsystem’s own custom 
> server processes.

The lock manager is not in the default path for many traditional Linux 
file operations, certainly.

Various apps can use range locks or local locking or other 
synchronization for that, but Linux does offer integrated lock 
management support.

I don't recall which Linux version first saw lock manager integration, 
but it was a while back. In RHEL clusters running GFS2 for instance, 
that DLM is a fundamental part of file access.

In a macOS cluster, the equivalent is Xsan: 
https://help.apple.com/serverapp/mac/5.0/#/apd6ec9abf60

There are other examples.

For many developers, the database and the database developers deal with 
this coordination, and not the app developer.  Just as RMS deals with 
this for coordinating punched-card access on OpenVMS.


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