> - Server: is that really our definition?
> I thought that "server" is what the glossary defines as "instance", and
> the thing called "server" in the glossary should really be called "host".
>
> Maybe I am too Unix-centered.
>
> Many people I know use "instance" synonymous to "cluster".
Currently our documentation uses 'server', 'database server', 'host',
'instance', ... in an indifferent way. Similar problem with
database/cluster. Now we have the chance to come to a conclusion about
preferred terms an their exact meaning. Definitions in the glossary
shall be the guideline, the documentation itself can adopt these terms
over time.
Here is my point of view. We have distinguishable things:
(1) (virtual) hardware
(2) an abstract structure of several object types, which models a
management system for data
(3) a group of closely related processes. They implement the internal
'business logic' or 'work flow' of (2).
(4) abstract data, which fits into (2)
(5) a physical representation of (4). Mainly and long lasting on disc,
but - partly - mirrored in RAM.
(6) client processes, which connect to (3)
IMO for (1) the two terms 'server' and 'host' both have their
justification, depending on the context. There are historical terms
('server-side', 'foreign server', 'client/server architecture', 'host'
or 'host name' for IP-specification, 'host variable') which cannot be
changed. Therefor we shall accept both with identical definition and use
them as synonyms. Independent from this, there are many paragraphs in
the documentation, where they are used in a misleading sense ('server
crash', '... started the server', 'database server'). They should be
changed over time.
For me, (3) is an 'instance' and (5) is a 'cluster'. There is a 1:1
relation between the two, because one 'instance' controls exactly one
'cluster'. But the 'instance' consists of processes and memory whereas
the 'cluster' of databases which resides (mainly) on disc.
Concerning (6) we are not interested in any hardware-question. We are
only interested in the processes, which connect to backend processes. We
should only define the term "Client process".
Kind regards, Jürgen
