The optional lastJournal parameter specifies the number of the last transaction journal file on which the operation is to be performed; for example, 9 (if you want to perform an operation on transaction journals up to and including db0000000009.log).
You can specify this parameter if the jdbutlib command line contains the backupJournal, dumpJournal, journalingRates, restoreJournal, or verifyJournal command or instead of the optional recoverTo or lastSerialNumber parameter if the jdbutlib command line contains the recover or restore command.