In CA SDM STDLOGs, one may encounter messages such as:
SEVERE_ERROR session.c 4268 Multiple responses received by zombie connection 1 (0x03BE4600) for session cnt:4E9B156CF8BFBC4A8C6DEAA83E1CD47B-720670003:0xb9f9440
The above message is tied to CA SDM STDLOG entries that indicate:
SEVERE_ERROR session.c 10188 Attempt to change id of active Session User1-1768827574:0x2900ce0 from 1768827574 to 972828143
SIGNIFICANT session.c 3990 This request took 4222693 milliseconds to complete. session id:0 login name:User1 htmpl name:delayed_server_response.htmpl
CA Service Desk Manager, releases 12.6 and onwards
Basically, whenever the webengine is encountering a delayed backend response (delay threshold is 20 seconds and is configurable in an NX.ENV variable per TEC1200339), the webengine will advise the end user with the delayed server response form and it saves the web connection as a "zombie" connection. Once a delayed response returns from the backend, the "zombie" connection is revived and readied to display output to the end user.
The concern from the above is when a given session or connection does not return a response in a timely manner or is experiencing a substantial amount of backend activity which further delays or even prevents a response.
Another possibility may also include environmental latency - there is a delay in network communication or database responsiveness.
Under such conditions, one should consider reviewing for a potential performance issue.
TEC473185: How may we identify performance issues in Service Desk and what type of data is helpful to Support to resolve these issues?
TEC1200339: Delayed Server Response Message