Derby is a pure Java relational database engine using standard SQL and JDBC as its APIs.

Derby functionality includes:

• Embedded engine with JDBC drivers
• Network Server
• Network client JDBC drivers
• Command line tools: ij (SQL scripting), dblook (schema dump) and sysinfo (system info)

IMPORTANT NOTICE:

If you are currently using Derby 10.3.1.4 or Derby 10.3.2.1, it is strongly
recommended that you upgrade to Derby 10.4.1.3 or 10.3.3.0 to avoid
any chance of database corruption due to an issue with multiple threads
accessing a database that is documented in DERBY-3347.

This bug can cause unrecoverable database corruption during periods of
heavy, multi-thread I/O operations. The error produced in the test case
used to diagnose the problem was:

ERROR XSDB3: Container information cannot change once written: was 0, now 80.

It is felt that other errors might also be generated when this type of
corruption occurs. The corruption message will most likely refer to page 0
of the container. For example:

ERROR XSDG1: Page Page(0 ,Container(0, 5856)) could not be
written...

This bug corrupts the pages on disk and can go unnoticed. If you do not
run database consistency checks regularly it is recommended you begin doing
so as soon as possible after the upgrade. To insure that corruption has not
already occurred in existing databases, after upgrade run the database
consistency check at least once to validate all tables in the database. This
process is documented at:

http://wiki.apache.org/db-derby/DatabaseConsistencyCheck

If the corruption has already occurred there is no guaranteed recovery of data
other than to recover from the last good backup. When doing so one should
also check that the previous backup did not also have the corruption.

In some cases one may recover data from the existing
database, depending on the extent of the corruption, but will require
by hand data recovery. Depending on the type of corruption this may
be successful or not. one should consult the Derby list if attempting
this recovery - no automatic software solution to this recovery exists.

Version 10.3.3.0 can be downloaded from:
http://db.apache.org/derby/releases/release-10.3.3.0.cgi

Version 10.4.1.3 can be downloaded from:
http://db.apache.org/derby/releases/release-10.4.1.3.cgi

For help or questions, please post to the Derby User list.
For instructions on how to subcribe and post to the Derby User list,
please see:

http://db.apache.org/derby/derby_mail.html