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From robert stephens <stephe...@acm.org>
Subject But Why Can't I Connect to toursDB --> Re: Lock on toursDB After App Disconnect Using org.apache.derby.jdbc.EmbeddedDriver
Date Wed, 24 Nov 2004 23:54:28 GMT
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.




On Nov 24, 2004, at 1:46 PM, Daniel John Debrunner wrote:

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>
> robert stephens wrote:
>
>> I understand that the org.apache.derby.jdbc.EmbeddedDriver does not
>> support simultaneous connections to a Cloudscape database
>
> Just to be clear, the embedded driver does support multiple 
> simultaneous
>  connections from within a single Java virtual machine. Derby supports
> multiple users, multiple connections, multiple threads, transactions,
> row locking etc.
>
> With the embedded driver the limitation is that only a single Java
> virtual machine can connect to the database files. The optional network
> server allows multiple connections to the database from multiple java
> virtual machines using DB2's JDBC universal driver.
>
> Dan.
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