Mbpctrefreshthresh
The mbpctrefreshthresh (megablock percentage refresh threshold) option is a number defining a threshold. When the percentage of IBM Spectrum Protect objects that are needed to describe any 128 MB megablock exceeds this value, the entire megablock is refreshed and the objects that were used to represent this area, in previous backups, are expired.
When you backup a virtual machine, data is stored on the IBM Spectrum Protect server in 128 MB units, called megablocks. If an area on the production disk changes and a new incremental backup is performed, a new megablock is created to represent the changes that were made to the previously backed up data. Because a new megablock can be created with each incremental backup, eventually the megablocks can adversely affect the performance of the IBM Spectrum Protect database, and therefore, adversely affect the performance of most IBM Spectrum Protect operations.
Use this option when estimating the amount of additional data that is backed up for each virtual machine. For example, when a 128-MB block of a production disk changes more than the percentage specified, the entire 128-MB block is copied to the server. The block is represented as a single IBM Spectrum Protect object.
Supported clients
This option is valid for clients that act as data
mover nodes that protect VMware virtual machines. To use this option, you must have a license
agreement to use IBM Spectrum Protect for
Virtual Environments: Data Protection for VMware.
Options file
This option is valid in the client options file (dsm.opt). It can also be included on the server in a client options set. It is not valid on the command line.
Syntax
Parameters
The minimum value you can specify is 1 percent, the largest value is 99 percent; the default is 50 percent.
Examples
Set this option to trigger a megablock refresh when 50 percent (or more) of the objects in a megablock on a production disk have changed:MBPCTREFRESHTHRESHOLD 50