The transaction and roll-back log files are used in database recovery. You can specify whether you want DP4 to maintain either or both of these logs. The roll-back file is only maintained on the disk whilst the database is being used, and is deleted when programs terminate normally. The transaction log is normally saved to a removable disk each time you take a backup of your database, and is then cleared from your hard disk.
The transaction log records each database transaction. The log records the transaction data, the nature of the change and the date and time the record is changed. This information can be viewed on screen for testing and audit purposes, and the roll- forward recovery process uses this information to update an earlier version of a database.
The roll-back log stores images of data before changes are made. If a power failure or system crash occurs, the roll-back log can be applied to the database to return the database to the state it was in before the changes were made.
A temporary log is used to improve performance if you do not use a transaction log.