SQL Exceptions, transport-level errors on SharePoint 2010 App Server

Question

SharePoint 2010 becomes inaccessible 2-3 times per day. It happens at approximately the same times: 8 PM, 1 AM and 1 PM. It is inaccessible for about 3-4 minutes and then comes back on its own.
During the time it is down, we see the following errors in the event viewer on the application server:
EventID: 5586 Task Category: Database -
Unknown SQL Exception 64 occurred. Additional error information from SQL Server is included below.A transport-level error has occurred when receiving results from the server.
(provider: TCP Provider, error: 0 - The specified network name is no longer available.)
EventID: 3 Task Category: None -
.Net SqlClient Data Provider: System.Data.SqlClient.SqlException: A transport-level error has occurred when receiving results from the server. (provider: TCP Provider, error:
0 - The specified network name is no longer available.)
EventID: 6398 Task Category: Timer -
The Execute method of job definition Microsoft.Office.Server.Search.Monitoring.HealthStatUpdateJobDefinition (ID f9db48f1-f115-47ab-99b6-552460cbb782) threw an exception. More
information is included below. A transport-level error has occurred when receiving results from the server. (provider: TCP Provider, error: 0 - The specified network name is no longer available.)
EventID: 8086 Task Category: Business Data -
The BDC Service application failed due to a SQL Exception: SQLServer host ums1spd1v. The error returned was: 'A transport-level error has occurred when sending the request to
the server. (provider: TCP Provider, error: 0 - An existing connection was forcibly closed by the remote host.)'
The SharePoint logs have errors during the same time period saying the same kinds of things: Sql exception raw message: A transport-level error has occurred when receiving results from the server,
The specified network name is no longer available, etc.
Our network administrator has looked at the issue and cannot find any network problems. 
He setup a continuous ping from the app server to the database server. 
Even during the times these errors are occurring, the app server is still able to reach the database server. 
However, you cannot ping the app server itself during this time.
Our database administer cannot find any SQL Server issues. 
There are no errors in the event viewer or the SQL logs on the database server.
In Central Admin, we can see that one or two jobs fail with SQL errors during the times these errors take place.
 It is almost always the “User Profile Service Application – User Profile Language Synchronization Job” and often the “Health Statistics Updating” or “Crawl Log Report for Search Application Search Service Application”. 
These jobs run successfully at many other times during the day.
Is there a good way to tell if the database, network or SharePoint itself is the root of these problems? 
The database and network guys say there are no problems in their areas, but all I can find in the SharePoint logs is that it can’t reach the database server.
Thank you for any suggestions you may have!

Answer 1

Since these seem to happen at very specific times, I would run a NetMon trace at that window to capture what is going back and forth (or perhaps the timer service is just unable to reach the SQL server).
Trevor Seward, MCC
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This post is my own opinion and does not necessarily reflect the opinion or view of Microsoft, its employees, or other MVPs.