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From Stanley Bradbury <bradb...@Mutagen.Net>
Subject Re: But Why Can't I Connect to toursDB --> Re: Lock on toursDB After App Disconnect Using org.apache.derby.jdbc.EmbeddedDriver
Date Thu, 25 Nov 2004 01:04:56 GMT
robert stephens wrote:

> ok, but that wasn't my main point - Please read the rest of my posting 
> enclosed again below!! Specifically please have a look at item --- 3 
> --- and ***** the real interesting part *****  and let me know if you 
> have any comments on what's going on.....................
>
> Problem Example ---------> For example, I can connect to the example 
> "derbyDB" database from App1 and can connecto to the example "toursDB" 
> from App2 but after disconnecting and quiting both App1 and 
> App2.............App2 is never able to start by itself and connect to 
> the "derbyDB" because "once upon a time" App1 had connected to it even 
> though App1 is no longer running.
>
> I'm doing this on MacOS X so there is a possibility that since they (I 
> think) try to share the JavaVM over multiple apps it could be that the 
> Apple JavaVM was still running.
>
> Also note that I am not doing any of this connecting from the command 
> line but always through one of 2 Java/GUI based apps with App1 being 
> DbVisualizer Free 4.1.1. which is a free Java app you can download 
> from http://www.dbvis.com/products/dbvis/index.html and App2 being Sun 
> Java Studio Creator which is downloadable from Sun at 
> http://wwws.sun.com/software/products/jscreator/
>
> However, I did try the following following to make sure all databases 
> and engines were shut down:
>
> --- 1 --- Using DbVisualizer 4.1.1 made a connection (per the 
> Apache/Derby doc) jdbc:derby:;shutdown=true and 
> jdbc:derby:pathTo_toursDB;shutdown=true
>
> --- 2 --- Re-booted MacOS X to make sure no Apple JavaVM was still 
> running
>
> ---3 --- Interesting experiment.......using the command line ij tool 
> (java org.apache.derby.tools.ij) I created a new testdb by doing ij> 
> connect 'jdbc:derby:testdb;create=true';
>
> I verified that Sun Java Studio Creator can connect just fine to this 
> newly created Cloudscape database testdb (and it does just fine) - 
> then I quit this application.
>
> I then connected to testdb with DbVisualizer 4.1.1 and it connects to 
> testdb just fine. I then click the DbVisualizer disconnect button and 
> quit the app.
>
> When I start Sun Java Studio again and try to connect to it again I 
> get a "Can't start database" Error message even after doing all the 
> reboot and jdbc:derby:;shutdown=true stuff above
>
> ***** the real interesting part ***** prior to connecting to testdb 
> from ANY app if I save a copy of the testdb/log directory, I am able 
> to get Sun Java Studio to connect to testdb if I swap back in the 
> original testdb/log directory and take out the testdb/log directory 
> that was present when the apps each connnected the first time.
>
> I'm thinking there is some info stored in the testdb/log/log1.dat file 
> that isn't getting cleaned up after disconnect somehow and this is 
> making Sun Java Studio Creator think the testdb (or toursDB) is still 
> open (some file is still open) or locked.
>
Hi Robert -

Without a doubt there is something odd going on here, your shutdown 
commands should clear the lock file to allow access by other JVMs.  
Without the error messages you receive I can only make guesses.  Can you 
get Sun Java Studio to present the the derby exception being thrown?  
The reason I ask is because of your test with swapping out the logs 
allows the database to boot.  This indicates there may be a recovery 
problem rather than a dual boot (lock file) problem.  The common connect 
error when multiple JVMs are involved is the dual boot exception that 
states something to the effect " Another instance of Cloudscape may have 
already booted the database".  From your log swapping test I assume this 
is not the problem and possibly you have run into a manifestation of the 
Mac OS X jvm problem described in the article at the following URL:    
http://www-1.ibm.com/support/docview.wss?rs=636&context=SSCRVP&q1=mac&uid=swg21180506&loc=en_US&cs=utf-8&lang=en
Even if your error message is not the one documented in this article you 
will need to set the property listed in order to use Derby on Mac OS X 
with java 1.4.2 . 

If this does not resolve the problem please post the exception that 
Derby throws (possibly recorded in the Java Studio logfile?) - it will 
indicate the nature of the problem.

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