Is the preempt option available in active standby ASA firewall setup with single context...somewhere i have read that same is available in active-active setup or active/standby setup with multiple context..
If i active the multiple context mode on product environnement with two ASA5520 in Active/Standby mode, what are the impacts on the the production?
If you need to change the ASA from single to multiple context mode, i would strongly suggest that you configure it during downtime, not during production hour. To change the mode, the ASA also needs to be rebooted.
Here is more information on changing the mode, and what you need to be aware in regards to your existing configuration: