You should always monitor the growth of your vCenter database. The database is collecting and storing information from the vSphere environment. Most of the database's growth is normally due to:
Logging events
Logging tasks that were executed
Collection of performance data
Wrong recovery settings
Wrong DB sizing (especially Oracle)
Performance data normally causes the greatest amount of growth but when you are troubleshooting growth problems, make sure that you know the source of the growth. One method to validate the source of database growth is to read the Determining where growth is occurring in the VMware vCenter Server database document, found at http://kb.vmware.com/kb/1028356.
There are times when truncating the database information is necessary. This should only be an option if you can determine the source of growth. Make sure you are in compliance with the business policies on data retention, and after you have determined that you are going to truncate...