David Johnson wrote:

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> The single mutex architecture, aimed at multiple machines sharing a
> common database file, imposes limits that are a pain in modern systems.
> This was a large part of the reason that Jim started the Vulcan
> project. Only one instance of the classic engine can actually do IO on
> the database at any time (unless I misread the papers). So long as one
> instance is doing I/O, all other instances are blocked.

I think you may have misread the document, or the document may have
misstated the issue. Each classic process has a separate file pointer,
so all can do I/O to the database at the same time. The only time one
classic process waits for another is when both require write access to
the same page. If you could give me a pointer to the document (Jim is
reasonably prolific), I'll try to clarify that point.


Regards,


Ann

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