Whenever a database needs to be restored due to a disk error, etc., use the database recovery utility. In this case, you need the following information:

• Backup file
• Unload log file (or system log file if the HiRDB system is run without unloading the system log)

Figures 19-1 and 19-2 show an overview of database recovery.

Figure 19-1 Overview of database recovery (operation involving unloading of the system log)

Explanation

You can restore the database to the following status:

• Status existing when the last backup was made
  To restore the database to the status existing when the last backup was made, you only need the backup file. No unload log file is needed.
  
• Most recent status (most recent synchronization point)
  To restore the database to the most recent status, you need the backup file and the unload log file that was created by unloading the system log after the last backup processing.
  

  Figure 19-2 Overview of database recovery (operation without unloading the system log)

  

Explanation

You can restore the database to the following status:

• Status existing when the last backup was made
  To restore the database to the status existing when the last backup was made, you only need the backup file. No system log is needed.
  
• Most recent status (most recent synchronization point)
  To restore the database to the most recent status, you need the backup file and the system log file that contains the system log output after the last backup processing.