As with any new concept, there are terms that must be defined as we intend to
use them. Each new term is defined here along with our definition of that term.
Keep in mind that our definition may differ from other definitions you already
know.
Basic Logging
Basic logging records all file changes without regard to the meaning of those changes. When a database is restored from a log file, these changes are used to update the database.
Transaction Logging
Transaction logging is a superset of basic logging. Besides the recording of file changes, markers are recorded to indicate groups of changes that, when completed, leave the database in a consistent state. Normally, only completed transactions are restored.
Log File
A log file is the file used to record changes to a database. Each database can have its own log file, or several databases can share a common log file.
Backup
Backups are the periodic saving of the system data on some external media. The purpose of the procedure is to have some means of restoring the data should the system fail and lose data. Each manufacturer has their own procedures for doing system backups. You should consult your system manuals for more detailed instructions on doing backups.
Restoration
Restoration is the action of restoring the contents of a database after an unexpected system failure. In this case, the database is restored from backups and the database restore command, dbrestore(C-1), is run with the database's logfile to bring the database back to a consistent state as close to the time of the failure as possible.