Full transaction processing offers maximum data integrity, however, at some expense to performance. Using the SUPPRESS_LOG_FLUSH option reduces overhead with transaction processing log file flushes, but at the expense of automatic recovery. Suppressing the log flush makes automatic recovery impossible. This keyword is typically considered only with the PREIMAGE_DUMP keyword described below.
Although automatic recovery is not available to PREIMG files, it is possible to perform periodic dynamic backups. By using the PREIMAGE_DUMP keyword, it is possible to promote PREIMG files to full TRNLOG files during the server dynamic dump process (see Dynamic Dump). The promotion to a TRNLOG file means a full transaction log (history of the file changes) will be maintained only during the dump process. This guarantees changes made to data while the backup is occurring is saved in these specially maintained transaction logs. The ability to dynamically backup user data files somewhat minimizes loss of the automatic recovery feature with this mode.