As tasks and events happen in vCenter Server they are logged in the VC database. After a while these tables can become quite large.
Prior to vCenter Server 4, customers wishing to prune their VC database down needed to do so manually. VMware provides an SQL script via KB 1000125 that allows administrators to delete old tasks, events, and performance stats. By the way, I am the author of that SQL Server purge script — fear my mad T-SQL skillz!
What a difference a vSphere makes… Now in vCenter Server 4, there is a simple administrative option to configure the retention period for tasks and events. By default, the data is retained indefinitely, but as you can see, it’s quite easy to set it up according to your needs: