Working with database threads in an embedded environment
As a rule, do not use Thread.interrupt() calls to signal
possibly waiting threads that are also accessing a database, because
Derby may catch the
interrupt and close the connection to the database. Use wait
and notify calls instead.
There are also special considerations when working with more than one
database thread in an application, as described in
Working with multiple threads sharing a single connection.
When queries, batches, and statements that wait for database locks run longer
than expected, you can use interrupts to stop them. If you do, the
connection will be closed and an exception will be thrown.
If you design an application whose database threads may see interrupts, you
should plan for the following behavior:
- If a thread is interrupted and the interrupt status flag is not
cleared before entering a
Derby JDBC call, or if the
thread is interrupted while inside a
Derby JDBC call, the
connection that is experiencing the interrupt will be terminated in the
- If a query fetches rows from a database table after the interrupt has
- If the execution of a new element in a batched statement is attempted
after the interrupt has occurred
- If an interrupt is received while a transaction is waiting for a lock
If the connection is terminated, the application thread will experience the
- The JDBC call will raise an SQLException with state "08000"
("Connection closed by unknown interrupt").
- Outstanding transactional work on that connection will be rolled
back, and all of its locks will be released.
- The connection cannot be used to execute any further JDBC calls.
On return from the JDBC call, the Thread.isInterrupted() method
of the thread will return true, whether or not an exception terminating
the connection was thrown. That is, even if
Derby does not heed an
interrupt, the flag will remain set on exit from the JDBC call.
- All other connections will remain open. This includes other
connections which the interrupted thread may be using. These
connections will remain open at least until the thread tries to
use one of its other connections. If the thead has neglected to
clear its interrupted status flag, this connection is also subject to
termination as described above.
- The application should normally be prepared to catch the 08000 exceptions,
discard the dead connection, clear the interrupted status of the thread, and
then restart the transaction in a new connection.