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From Aristedes Maniatis <...@maniatis.org>
Subject Re: Cayenne and H2 on the desktop
Date Wed, 21 Oct 2009 04:40:34 GMT
On 21/10/09 2:56 PM, Eric Lazarus wrote:
> About the meaning of 'embedded': I think that the 2nd option has a
> server process running tcp on some port number in the 9000's. Does this
> count as an 'embedded' database? I assume not.
>
> Also, what happens in the
> first case if the user opens two instances of the program on his
> desktop. Does not each instance access the same files ? What kind of
> locking is implemented in that case?

I don't use H2, but for Derby:

* you can 'embed' the Derby jar within your own application jar or you can run it standalone
* if you embed it or if it runs standalone, you can have it open a TCP socket and communicate
with it just as if it was a separate application. Other apps can also connect.
* if you embed it, you can also use a different JDBC connector to connect directly without
a TCP socket. That might be more secure, but it doesn't make anything simpler (or faster).
* whatever you do, you cannot have two database engines (standalone or embedded) using the
same files on disk. I'd guess that holds true for any database in existence today.

Ari

-- 

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Aristedes Maniatis
GPG fingerprint CBFB 84B4 738D 4E87 5E5C  5EFA EF6A 7D2E 3E49 102A

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