This is an extract I have found in the past in soe CommVault Documetation, I have had instances when I could not do what it suggests, but this is a standard tweak we do on all CommServe installations when we have lots of free mem:
After installing the CommServe Software, the SQL Server instance COMMVAULT requires specific settings. In the Memory tab, the dynamically configured Maximum memory should be 50% of the physical memory available in the CommServe machine. The Memory tab is located in the Properties screen for the CommVault instance, and is accessible from the SQL Enterprise Manager.
Obviously this could be tweaked a lot more if you have the ram.