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Object documentationVolume Expiration Period Locate this document in the navigation structure

 

The volume expiration period for backups of the Oracle database is defined by the init<DBSID>.sap parameter expir_period. This specifies the period in days during which a volume is locked, that is, cannot be used. When the period expires, you can reuse the volume for a backup.

Example Example

expir_period = 28 means that writing to a volume is possible 28 days after the volume was mounted and used. For example, if you use a volume on Monday 1st July, you cannot use it for another backup until Monday 29th July.

End of the example.

The start time of BRBACKUP or BRARCHIVE determines the first day of the lock for all volumes used for a backup. The time when the volume was first written to does not matter. The expiration period always expires at midnight (that is, 24:00 using the 24-hour clock) of the last day of the lock.

Recommendation Recommendation

SAP recommends an expiration period of at least 28 days (the default value is 30 days).

End of the recommendation.

Recommendation Recommendation

If you set an expiration period of 0 days, this means that the volume is not locked. The volumes can be overwritten on the same day. Therefore, do not set expir_period to 0.

End of the recommendation.

Structure

The current value of expir_period is decisive for whether or not a volume is locked, not the value of the parameter during the backup. This means that the backup volumes are locked for n days after the last backup operation, where n is the current value of expir_period. If the value of expir_period is changed, the expiration period for all volumes is automatically changed.

Volumes can be locked physically and logically:

  • Physical lock

    The volume generation date specified on the volume label is decisive for a physical lock. This generation date is determined when the volume label is written (when a backup on this volume was started). A volume is locked physically when the system checks the volume label and finds that the expiration period for the volume has not ended yet, that is, the value of the current date is less than the total of the volume generation date stored in the volume label and the value of expir_period.

  • Logical lock

    The internal information in the BRARCHIVE or BRBACKUP logs is decisive for a logical lock. The logs are updated when a database file has been backed up successfully. A volume is locked logically when the automatic volume management system checks the volume and finds that the expiration period stored internally has not ended yet; the value of the current date is less than the total of the volume generation date stored in the BRBACKUP or BRARCHIVE logs and the value of expir_period. Under certain circumstances, discrepancies may occur between the physical and logical locks.

You can unlock volumes as follows:

  • Unlocking a physically locked volume

    During a backup, the volume label was written to the volume but the backup was terminated before the first database file could be written to the volume.

    This means that the volume is locked physically but not logically. It is selected from the list by the automatic volume management system – with volume_backup or volume_archive – but is rejected when the physical volume label check takes place. The volume can be reinitialized (with the same name) in order to cancel the physical lock, as follows:

    1. Temporarily set the init<DBSID>.sap parameter expir_period to 0, to circumvent the physical lock.

    2. Start BRBACKUP or BRARCHIVE, for example, as follows:

      brbackup|brarchive -i -v <volume name>

    3. Reset the expir_period parameter to its previous value.

    When performing this operation, do not use the -i force option, as this causes the volume use count stored in the volume label to be lost.

  • Unlocking a logically locked volume

    A volume was reinitialized before the expiration period ended (for example, with the option -i force). This means that the volume is no longer locked physically. However, it is not selected by the automatic volume management system because it is still locked logically.

    If you still want to use this volume before the logical lock has expired, you can switch off automatic volume management temporarily by mounting the volume on the backup device and starting a backup with the following command:

    brbackup|brarchive -v SCRATCH

For more information, see: