John Embretsen wrote:
=== SNIP ===
<quote 1 from "Activity notes", p.6 (8)>
A client program is often created to allow database access and updates
from multiple computers on the network.
</quote>
I don't think this statement is correct. It is not the "client
program" that allows access from multiple computers, it is the server
framework that does this. Would you like to rephrase?
<quote 2 from "Activity notes", p.6 (8)>
Derby's two architectures have caused confusion for some new Derby
users. They mistakenly think that embedded is a single user
configuration. Not true. The embedded driver supports multiple
simultaneous connections, performs locking and provides performance,
integrity and recoverability.
</quote>
I think this is still confusing. I think you should add a comment
saying that the embedded driver must *not* be used to access the same
database from more than one JVM simultaneously. The multi-user
capabilities you are describing are (as far as I know) only valid if
all users use the same JVM/Derby system (i.e. the same instance of the
embedded driver), or if no users using different JVMs/Derby systems
access the same database at the same time.
Hi John -
Thanks again for your attention and feedback. Both suggestions are well
taken.
The sentence about the reason to create a client program is not well
constructed and is inaccurate. I also see that it does not carry the
message I intended and I will rephrase it.
The other note is what I think of as an 'endorsement of the embedded
architecture'. I included it to get people thinking / questioning along
the lines you are, I have been successful in that regard. I think it an
important endorsement to make because I have seen many people new to
Derby avoid embedded without really thinking it through. It is my sense
that the copious warnings about 'double booting' scares them away from
embedded. After working with Derby for awhile these people see that the
embedded driver fully supports their need and is a cleaner and faster
implementation. I wanted to plant that seed of an idea.
It is arguable that the topic does not belong in an introductory
document at all because it deals with system architecture as well as the
specific meaning of terms like 'single-user', 'client-server',
'networking' and 'interprocess communication'. Clearing up the
confusion is out of the scope of this document. Your suggestion,
however, has me thinking I should draft a short paper on the topic that
can be referred to when questions like yours are raised and will begin
working on this. Do you think this will help with the issue you raise?
I hesitate to include the standard caution about access from
multiple-JVMs as I perceive this as contributing to the mind-set that
using the embedded driver is limiting.
I would really like to hear your thoughts on this and maybe begin a new
thread on the topic of when to use Network Server and when the embedded
driver is sufficient. It seems there is enough in this topic for a
lively discussion.
