An important part of JE's transactional guarantees is durability. Durability means that once a transaction has been committed, the database modifications performed under its protection will not be lost due to system failure.
JE supports a normal recovery that runs against a subset of your log files. This is a routine procedure used whenever your environment is first opened upon application startup, and it is intended to ensure that your database is in a consistent state. JE also supports archival backup and recovery in the case of catastrophic failure, such as the loss of a physical disk drive.
This book describes several different backup procedures you can use to protect your on-disk data. These procedures range from simple offline backup strategies to hot failovers. Hot failovers provide not only a backup mechanism, but also a way to recover from a fatal hardware failure.
This book also describes the recovery procedures you should use for each of the backup strategies that you might employ.
For a detailed description of backup and restore procedures, see the Getting Started with Berkeley DB, Java Edition guide.