Volume Expiration Period 

The volume expiration period is defined in days with the init<DBSID>.sap parameter expir_period (see expir_period).

expir_period = 2 means that writing to a volume (tape) is possible on the second day after the volume has been mounted and used. If you use a volume on Monday, for example, you cannot use it for another backup until Wednesday.

The start time of BRBACKUP/BRARCHIVE determines the first day of the lock for all volumes used for a backup. The time when the volume was initialized does not matter.

The expiration period always expires at midnight (12:00 a.m.) of the last day of the lock.

If you set a 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 zero.

SAP recommends a expiration period of at least 14 days, 28 days would be even better (the default value is 30 days).

The current value of the parameter 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, n being 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. 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, i.e., 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 .

The internal information in the BRARCHIVE/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/BRARCHIVE logs and the value of expir_period. Under certain circumstances, discrepancies may occur between the physical and logical locks.

Example 1

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 ( 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.

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

Example 2

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 want to use this volume nevertheless (before the logical lock has expired), you can switch off automatic volume management temporarily, for example, by calling brbackup|brarchive -v SCRATCH and mounting the volume on the backup device.