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  1. #1
    Join Date
    Aug 2003

    Red face Unanswered: DB2 Backup/Recovery db cfg parameters, what it mean ?

    Hi All,

    Can anyone help me to understand these configuration parameters.

    1. Number of database backups to retain (NUM_DB_BACKUPS) = 12
    2. Recovery history retention (days) (REC_HIS_RETENTN) = 366

    Q1. Does it means I can't restore 13th day old data ? (if I am taking regular offline backups daily )
    Q2. what if the entry in history file is deleted (not in history file ) , will I be able to restore the database ?

    Awaiting for Quick reply


  2. #2
    Join Date
    Jul 2003
    Austin, TX, USA



    This is an extract from the online documenation.

    Number of Database Backups configuration parameter - num_db_backups
    Configuration Type
    Parameter Type
    Configurable online
    Propagation Class
    Transaction boundary
    Default [Range]
    12 [ 1 -- 32 768]
    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, TSM). The next database backup will prune the expired entries from the recovery history file.

    Recovery History Retention Period configuration parameter - rec_his_retentn
    Configuration Type
    Parameter Type
    Default [Range]
    366 [ -1; 0 -- 30 000 ]
    Unit of Measure
    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.

    If value of this parameter is -1, the recovery history file can only be pruned explicitly using the available commands or APIs. If the value is not -1, the recovery history file is pruned after every full database backup.

    The the value of this parameter will override the value of the num_db_backups parameter, but rec_his_retentn and num_db_backups must work together. If the value for num_db_backups is large, the value for rec_his_retentn should be large enough to support that number of backups.

    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.

    When a database backup is marked as expired in the history file, any corresponding file backups linked through a DB2 Data Links Manager will be removed from its archive server.

    Hope this helps



    Ask the experienced rather than the learned

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