BAR_SIZE_FACTOR configuration parameter

Use the BAR_SIZE_FACTOR configuration parameter to augment the estimate for the size of a backup object, before the backup.

onconfig.std value
Not in onconfig.std.
default value
0
range of values
0 = The estimated size of the backup is not augmented.
Positive integers = The percentage of the original backup size.
takes effect
When the database server starts
When you reset the value dynamically in your onconfig file by running the onmode -wf or equivalent SQL administration API command.

Usage

The estimate is handled before the backup and is calculated so that the storage manager can allocate the storage media appropriately. Because the backup is done online, the number of pages to back up can change during the backup. Some storage managers are strict and if the backup estimate is too low, the backup results in an error.

The value of BAR_SIZE_FACTOR is taken as percentage of the original backup object size, and then added to the estimate, before communicating it to the storage manager. BAR_SIZE_FACTOR is used only for dbspace backup objects, not for logical log backup objects.

The formula used for calculating the new estimated backup object size is: 
new_estimate = original_estimate x (1 + (BAR_SIZE_FACTOR / 100))
The value to which you set this parameter in a specific server environment depends on the activity on the system during backup or archive. Therefore, determining the value needs to be based on the individual experience with that system.