We are running a java application using embedded H2 databases and ran into data loss situation that we can not explain. It appears as if the database reverted to a previous state - or that data wasn't written to file for hours.
Setup: Java 8 client software running on tablets(Microsoft Surfaces), using a file-based embedded H2 database for local storage (H2 version 1.4.196). The database is started in a cluster with a secondary mirror database (HA-JDBC version 3.0.3). Situation: Entries were inserted into the client-devices' database, updated and later also send the server. After a client-software restart that data was suddenly gone from the client. In analysed cases there was a previous point where our application was suddenly terminated without proper shutdown procedure. Sometimes hours between the creation of the data, the improper shutdown and then the restart, sometimes closer in range of minutes. Our own logging indicated that the missing data was actually saved successfully in the client-device's H2. Further, the server's SOAP service had received the data, proving that the data had to exist on the client at one point. We quickly received the client-device's databases from the customer and it did not contain said data despite our logfile inidating that it had been created and even updated afterwards. It nearly appears as if the data was never written to the database file. But that it was synchronized to the server is proof that at one point the data had to be query-able when determining what data to send to our server application. Notes: Master and mirror database are ensured to be equal in content before starting the client-device database cluster. Should they not be equal the mirror will not be added to the cluster. Further, the cluster uses no synchronization(passive strategy) so it can't be an out of date mirror database causing a revert. The customer had in the past already problems with corrupted database files due to power loss and improper shutdown of our application. However in these data-loss cases the database started as normal and did not complain about corrupted files. Other customers have not reported similar problems despite running similar setups, e.g. also using Microsoft Surfaces. Questions: What could lead to the database seemingly reverting to a previous state? Are there known problems related to running in a HA-JDBC cluster? Can an unexpected shutdown of the embedded H2 lead to data reverting in a way it is hours old? Are there already fixed bugs or similar situations that can lead to something like the described problem? Is there any kind of long-living H2 memory cache that never gets writte to the actual file for quite a while and is lost on power loss? (I assume not, judging by the documentation) Is it possible that the database "repaired" itself, somehow loosing data in the process - or got corrupt in a way that a previous version of data reapears? What other steps could we do to further trace where the problem is comming from? Thanks in advance, Christian Dirks -- You received this message because you are subscribed to the Google Groups "H2 Database" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/h2-database/6b51a950-b6e3-4c61-81fb-c7ca925d973an%40googlegroups.com.
