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From "Flavio Palumbo" <f.palu...@silmasoftware.com>
Subject R: R: connection strange behavior
Date Tue, 01 Aug 2006 08:21:57 GMT
Hi Stanley,

thanks for your responses ;-))

I looked the links you provided but I think my scenario is different.

I wrote a stand alone application (like a VB .exe, not WEB) that is shared
on a local network because the directory where the jars resides is shared
for all the network users ; inside this directory is defined a derby
database with 2 user tables, and I'd like that the access to these tables
was shared for all the users that concurrently run the application.

The first time I tried to use the embedded driver, but this way doesn't
share the database ; thus I tried to implement the network server making it
start every time a user starts the application but in this way I found the
problem mentioned in earlier mails.

I think a right way could be start the server once, in a separate jvm, when
the first time the application is called and then let it up and running
until the PC is shut down.

What you think about this ??

Another problem is that I don't know how start the server from inside the
application in a separate jvm.

Could you give some other hints or code snippet ??

Thanks a lot
Flavio


> -----Messaggio originale-----
> Da: Stanley Bradbury [mailto:Stan.Bradbury@gmail.com]
> Inviato: lunedì 31 luglio 2006 21.15
> A: Derby Discussion
> Oggetto: Re: R: connection strange behavior
>
>
> Flavio Palumbo wrote:
> > Hi all,
> >
> > sorry for the long delay of this response but I spent a little
> holiday ;-))
> >
> > Could you please provide some code examples ?? specially when you say :
> >
> > "Usually it is done by defining a global datasource that is started when
> > the server starts.  Then by setting the property
> > derby.drda.startNetworkServer to true in the JVM arguments that are set
> > at Server startup the Network Server will also start.  It is recommended
> > that he Network Server be started and shutdown when the server starts
> > and shutdowns and also that a security manager be used to secure the
> > environment."
> >
> > Thanks a lot.
> >
> > Flavio
> >
> >
> > Flavio Palumbo wrote:
> >
> >> Hi,
> >>
> >> thanks everybody for the suggestions provided ;-))
> >>
> >> Now I try to explane my goal :
> >>
> >> - I have an application shared in a local network environment (one jar
> >>
> > file
> >
> >> where every client in the network can double
> >>   click and start it in a new jvm)
> >> - when the application starts, I'd like to start
> (automatically) the derby
> >> network server
> >> - every client opens a new connection to the server
> >> - when the client finishes its work, it closes its own connection, shut
> >>
> > down
> >
> >> its instance of the application and closes
> >>   its jvm
> >> - the last client closes the server
> >> - note that the shared derby DB is in a network shared directory
> >>
> >> to achieve the aim explaned above I wrote a test case where I
> do something
> >> different : every time the application starts,
> >> it starts a new instance of the network server and a new
> connection. I did
> >> this cause I don't know how to start the network server only once (when
> >>
> > the
> >
> >> first client starts the application) and also don't know how to be
> >>
> > informed
> >
> >> when the last
> >> client closes the application.
> >> This kind of test seems to work ; if I open the application in two
> >>
> > different
> >
> >> shells of my PC (two jvm) I can read and write into the same
> table of the
> >> same db, thus it seems to be shared as I desire.
> >> But following the tests I encountered some impredictable errors (not
> >>
> > always
> >
> >> the same error, data seems to be lost, strange exceptions ...)
> making me
> >> think maybe this is not the right way :-((
> >>
> >> Thanks for any suggestion
> >> Flavio
> >>
> >>
> >> === SNIP ========
> >>
> > Hi -
> > Ouch, You are correct when you say:
> > " (not always the same error, data seems to be lost, strange exceptions
> > ...) making me think maybe this is not the right way "
> > Strange exceptions and data loss is what happens when database I/O is
> > performed across a network.  Your configuration is causing
> these problems:
> > " - note that the shared derby DB is in a network shared directory "
> >
> > The disks must be local to the machine running the Derby engine.
> >
> > A centralized server architecture will handle this.  Start your server
> > and the Network server on the machine where the database files reside
> > and have the applications connect either to the server via whatever
> > protocols it supports or via the Network Server using the client
> > driver.  How you set this up depend on the server you are using.
> > Usually it is done by defining a global datasource that is started when
> > the server starts.  Then by setting the property
> > derby.drda.startNetworkServer to true in the JVM arguments that are set
> > at Server startup the Network Server will also start.  It is recommended
> > that he Network Server be started and shutdown when the server starts
> > and shutdowns and also that a security manager be used to secure the
> > environment.
> >
> > HTH
> >
> >
> >
> >
> > -----------------------------------------------------------
> > Il presente messaggio non costituisce un impegno contrattuale
> tra SILMA S.r.l. ed il destinatario.
> > Le opinioni ivi espresse sono quelle dell'autore.
> > SILMA S.r.l. non assume alcuna responsabilita riguardo al
> contenuto del presente messaggio.
> > Il messaggio è destinato esclusivamente al destinatario.
> > Il contenuto e gli allegati sono da considerarsi di natura confidenziale
> >
> > Nel caso abbiate ricevuto il presente messaggio per errore
> siete pregati di comunicarlo
> > alla casella segreteria@silmasoftware.com.
> >
> >
> >
> I'm not sure of the architecture you are using.  My response assumed
> that you were using an Application Server like Geronimo, Tomcat , etc.
> These each have their own methods for defining Global datasources.  You
> can find writeups that contain instructions on doing this under 'Product
> Writeups' on the Apache Derby Resources page:
> http://db.apache.org/derby/integrate/index.html#products
>
> If you are writing your own Server and want to add datasource
> functionality to it you might want to use the system that Tomcat uses:
> |commons-dbcp| (http://jakarta.apache.org/commons/dbcp/).
>
> Is this what you needed ??
>


-----------------------------------------------------------
Il presente messaggio non costituisce un impegno contrattuale tra SILMA S.r.l. ed il destinatario.
Le opinioni ivi espresse sono quelle dell'autore.
SILMA S.r.l. non assume alcuna responsabilita riguardo al contenuto del presente messaggio.
Il messaggio è destinato esclusivamente al destinatario.
Il contenuto e gli allegati sono da considerarsi di natura confidenziale

Nel caso abbiate ricevuto il presente messaggio per errore siete pregati di comunicarlo
alla casella segreteria@silmasoftware.com.


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