In a CASO environment, communications that occur between managed Backup Exec servers and the central administration server can sometimes be disrupted even if network communications are normal. If job-related communication disruptions occur between a managed Backup Exec server and the central administration server, the managed Backup Exec server's communication status changes from Enabled to Stalled or No Communication. The jobs waiting to be processed by the managed Backup Exec server are held in the managed Backup Exec server's job queue until the communications are restored.
You can set the amount of time that Backup Exec waits before changing the managed Backup Exec server's status if it becomes unresponsive. When a managed Backup Exec server's status changes to Stalled or No Communication, the central administration server changes how it handles current and future jobs delegated to the stalled managed Backup Exec server.
For example, if communications from a managed Backup Exec server are not received at the central administration server after the set amount of time, the central administration server changes the Backup Exec server's communication status to Stalled. Job delegation to the managed Backup Exec server is suspended as it continues to wait for the managed Backup Exec server to return to an Enabled status. Jobs are delegated to other managed Backup Exec servers that are represented in the destination storage device or Backup Exec server pool.
CASO continues to monitor the amount of time during which no communications are received from the managed Backup Exec server. After a set amount of time passes after a Stalled status appears, CASO changes the status of the managed Backup Exec server to No Communication. CASO marks the jobs as Failed, and then begins job recovery by invoking the custom error-handling rule Recovered Jobs for any job that is active at the time the No Communication status appears.
Please refer to following Technote for more details ::
http://www.symantec.com/docs/HOWTO73648 (What happens when CASO communication thresholds are reached)
Hope this helps.
