Hi Fabio,
this error is thrown at top level (in a WorkerThread), but it is not an SQL Exception, neither an SDMSException or any other Exception.
It is also not a StackOverflowError or OutOfMemoryError, but some other Error.
The Error is logged in the log file, together with a stack trace. You'll have to look there for more information.
If you have the sources somewhere on your system, you can grep for the error number. They should be unique (but we make a mistake sometimes).
Hence, something like
cd $SDMSHOME/src/server
find . -name '*.java' | xargs grep "03909211653"
gives you the file that is responsible for throwing the error. In this case
ronald@oncilla:~/schedulix-2.10/src/server$ find . -name '*.java' | xargs grep "03909211653"
./WorkerThread.java: n.result.setError(new SDMSOutputError("03909211653", "Internal Error ! Contact your System Administrator !"));
BTW: Restarting the server was the best you could do in this case.
Best regards,
Ronald