How come when you select VRDB generation now it finishes within 20 minutes yet if you select when idle and leave it alone it can take longer, is it to do with how they are prioritised or something?
ps is it normal for a nearly constant HDD activity light while it is running?
You have answered your own question, when you select Generate Now it starts and continues uninterrupted until completion, the Run when Idle is a background process that may have many interruptions.
Personally I set mine to run when the screensaver is running and since I don’t use a screen saver it will never run. So I do a manual Generate Now as part of my regular system maintenance.
How is it to check and obtain information on the files it is going to include in the database without accessing your hard drive, so yes it is normal to see disk activity in the form of your HDD led when generating the VRDB.
thankyou for the info, I did your suggestion prior to running it and it is far better 
Your welcome.