REC_HIS_RETENTN

建议将这个文件控制在30M以内，最好是20M左右
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rec_his_retentn - Recovery history retention period configuration parameter Configuration Type Database Parameter Type Configurable Default [Range] 366 [ -1; 0 -- 30 000 ] Unit of Measure Days

This parameter is used to specify the number of days that historical information on backups should be retained. If the recovery history file is not needed to keep track of backups, restores, and loads, this parameter can be set to a small number.

8 If value of this parameter is -1, the number of entries indicating full database backups 8 (and any table space backups that are associated with the database backup) will correspond with the 8 value specified by the num_db_backups parameter. 8 Other entries in the recovery history file can only be pruned by 8 explicitly using the available commands or APIs.

No matter how small the retention period, the most recent full database backup plus its restore set will always be kept, unless you use the PRUNE utility with the FORCE option.