Start backup mode in order to determine the definitive backup set needed at this point in time.
This method determines the last file in the backup set, which is the last log file in the environment at this point in time. Following this method call, all new data will be written to other, new log files. In other words, the last file in the backup set will not be modified after this method returns.
WARNING: After calling this method, deletion of log files in the backup set by the JE log cleaner will be disabled until {@link #endBackup()} is called. To prevent unbounded growth of disk usage, besure to call {@link #endBackup()} to re-enable log file deletion.Additionally, the Environment can't be closed until endBackup() is called.
@throws com.sleepycat.je.rep.LogOverwriteException if a replicationoperation is overwriting log files. The backup can not proceed because files may be invalid. The backup may be attempted at a later time.
@throws EnvironmentFailureException if an unexpected, internal orenvironment-wide failure occurs.
@throws IllegalStateException if a backup is already in progress