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Posted by Xandy Johnson on Jun 28, 2007
Apache Derby is a pure-Java, Open Source, relational database derived from IBM's Cloudscape. In the past couple weeks it has made two significant advances. First, the project made a beta available of the upcoming 10.3 release. The 10.3 release includes security enhancements, language-based ordering, other features, bug fixes, and performance enhancements. Second, Egil Sørensen, a student at the Norwegian University of Science and Technology, submitted his thesis work on replication and availability, including a prototype implementation.
The 10.3 release of Apache Derby is scheduled to be released on July 16. A beta is now available. In addition to performance enhancements and bug fixes, the major new features are:
Minor features include:
Egil Sørensen has submitted his MS thesis work to add hot standby replication functionality to Derby.
By implementing a hot standby scheme in Apache Derby several features are added. The contents of the database is replicated at run time to another site providing online runtime backup. As the hot standby takes over on faults availability is added in that a client can connect to the hot standby after a crash. Thus the crash is masked from the clients. In addition to this, online upgrades of software and hardware can be done by taking down one database at the time. Then when the upgrade is completed the upgraded server is synchronized and back online with no downtime.
A fully functional prototype of the Apache Derby hot standby scheme has been created in this project using logical logs, fail-fast takeovers and logical catchups after an internal up-to-crash recovery and reconnection.
The prototype was submitted as a patch against the 10.2.2.0 release (i.e. the latest production release), but it has already been ported to the trunk. There is another issue requesting that replication functionality be added. As a result the patch may receive consideration for 10.4.
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The H2 Database Engine supports these features since quite a long time.
Still interesting, specially hot standby (called 'Clustering' in H2).
But H2 sucks with multiple connections as it's primary role now to hold single-user connection.
> sucks with multiple connections
Maybe the problem is the default settings? The default transaction isolation level of H2 is SERIALIZABLE. For Derby, it is READ COMMITTED. H2 supports that as well. To try it out, use the following database URL: jdbc:h2:~/test;LOCK_MODE=3.
Thomas, is the "Lock Mode = 3" feature now stable? Last time I asked this question, you said that it was experimental. Why don't you let the "Read Committed" mode be the default transaction level like other DBs?
Read Committed is stable now. I will think about making it the default, good idea!
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