Details: Developer dashboard is a new feature in SharePoint 2010 that provides information on the performance and tracing that can be used to monitor the page during render. By default its turned off. You can turn it on using either stsadm / powershell / code. You can use the below code to trigger the developer dashboard.
SPFarm farm = SPFarm.Local; SPWebService context = farm.Servers.GetValue
(); context.DeveloperDashboardSettings.DisplayLevel = SPDeveloperDashboardLevel.OnDemand; context.DeveloperDashboardSettings.Update();
As marked in the pic above, Developer Dashboard can be toggled to On/Off based on the SPDeveloperDashboardLevel. There are 3 states of the Levels, On/Off/OnDemand. A Turned-On dashboard would like as shown below.
Alternatively, you can turn it on using stsadm commands as shown below:
Set to 'On Demand' - displays an icon on top right hand corner for toggle
stsadm -o setproperty -pn developer-dashboard -pv ondemand
Set to 'On' - Always displayed
stsadm -o setproperty -pn developer-dashboard -pv on
Set to 'Off' - Turned off
stsadm -o setproperty -pn developer-dashboard -pv off