This parameter specifies the number of database backups to retain for a database. After the specified number of backups is reached, old backups are marked as expired in the recovery history file. Recovery history file entries for the table space backups and load copy backups that are related to the expired database backup are also marked as expired. When a backup is marked as expired, the physical backups can be removed from where they are stored (for example, disk, tape, ADSM). The next database backup will prune the expired entries from the recovery history file.
When a database backup is marked as expired in the history file, any corresponding file backups linked through a DataLinker will be removed from its archive server.
The rec_his_retentn configuration parameter should be set to a value compatible with the value of num_db_backups. For example, if num_db_backup is set to a large value, the value for rec_his_retentn should be large enough to support that number of backups.