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From Aristedes Maniatis <>
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.



Aristedes Maniatis
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