Yes. There has to be a transaction log, because if uncommitted changes have been written to disc and the system breaks it has to be able to undo those changes when it comes up again - and roll-back of uncommitted transactions is carried out based on the uncommitted changes recorded in the transaction log. Also, when the system breaks there may be a transaction that has been committed and some of whose updates are recorded only in RAM store and in the transaction log (because a checkpoint hasn't yet occurred since that transaction was committed) - and recovery when the system comes back up has to ensure that those updates are applied to the database records, so it has to retrieve those updates from the transaction log.