The security and integrity of a database is a very important concern in database management. If one data item is invalid, the entire database can be affected. If all the data values are correct, then there is data integrity.
These are some of the safeguards used by DP4 to preserve data integrity:
The transaction log records each database transaction. The log is used in roll-forward recovery to update an earlier version of a database where the current version is no longer valid.
The roll-back log stores images of data before changes are made to your database. If you experience a temporary failure such as the loss of power, you can apply the roll-back log to the database, to return the database to the state it was in before the changes were made.
When the user changes the value of a field, the value is checked against the type defined on the database, and the upper and lower bounds. See (field definition). The validation is applied automatically, independently of any validation carried out by your program.
Each time you add or amend a record, the referential integrity rules defined for a table are checked. If the rules are violated, a message is returned.
Where two users attempt to update the same record at the same time, the DP4 change verify mechanism ensures that an appropriate action is taken, and that one of the users is given priority over the other.
Facilities are included to back up the database and the transaction log. The user is prompted to take a backup at the intervals you specify (usually once a day)
A periodic check can be run to ensure that database integrity is maintained. The system user is prompted to run this utility at the intervals specified in the configuration.
When users log on, the database manager only allows them to see fields and records that match their read access level, and to change records that match their write access level. Access control can also be applied to the entire database, or to individual programs and menus.
A user log records the activities of each user.