Hello karpa08 ,
The connection can be closed on client side or server side, the PM setting is just for client side, on gateway side, navigate to menu "Tasks" > "Users and Authentication" > "Manage Administrative User Account Policy" > set "Gateway Session Expiry" to a value you prefer (1~1440 minutes)
For older version of CA API Gateway (9.0 or below), the menu path should be "Tasks" > "Manage Account Polices" > "Manage Administrative User Account Policy"
Regards,
Mark