Symptoms

We're seeing some performance issues where, when the services haven't been used in some time (e.g. 6-9 hours or so, the downtime between overnight PST and the next morning GST), users that attempt to access the worklist webpart in SharePoint or SmartForms will experience latency in the screens coming up or they will timeout and never appear. We've also noticed that even though certain parts of the system will be performing normally, others will not (e.g. users are using SmartForms and the worklist web part, but visiting the Designer URL will timeout the browser or you'll see each part of the interface load individually). Furthermore, we see users that haven't used K2 before will consistently experience a slowdown/timeout when they initially attempt to access any K2 resources.
 

Diagnoses

The issue was caused by K2 SmartForms Application Pool is recycled during that time that the user tried to access the system. Although the App Pool Recycle is disabled in IIS Setting, but having the Idle Time-out (minutes) set to 1440 that means that the process will drop and release all memory when no action has been asked by the web application.
 

Resolution

We changed the setting the Idle Time-out (minutes) to 0 for SmartForms Application Pool resolved the issue. You will need to monitor server’s memory over time since the application pool is set to be not recycled.