Intermittent TCP connections reset(Why SQL client does not response keep alive)?

Question

Hi experts,

  We run SAP on SQL and we found intermittent TCP connections reset from time to time. We created a case in MS CSS and they indicated sometimes SQL clients does not response TCP keep alive packets on some specific connections? What happen? Please help.

 

Answer 1

I am not an expert on this, but this MSDN blog discusses tracing down a similar problem and a workaround used until the main problem could be resolved.

http://blogs.msdn.com/b/dataaccesstechnologies/archive/2010/06/18/using-network-trace-to-troubleshoot-intermittent-connectivity-issues.aspx

From that blog you will see that it is not real simple to identify the root cause, but  "...we were able to implement a work around by increasing the “TcpMaxDataRetransmissions” setting to a higher value."

Here are some instructions: http://support.microsoft.com/kb/170359 

Something to look into.

RLF

PS - I used to manage a cluster of SAP servers (R3, so it was a while back) and at that time the network load was pretty light.  From my experience it is unlikely that SAP itself is the problem, although I do not know the current client setting.

Answer 2

Hi Russell,

  Thanks for your reply. In fact, I had already read that blog. I created a case in SAP OSS and I got the same response.

  Actually, I tried that before. Increasing keep alive interval may solve the problem if it is a idle connection. However,  I found TCP connections reset  intermittently happened on active connections sometimes.

  Anyway, I will try it again first.

Answer 3

Of course, if there is a hardware/software problem that is resulting in resets of a connection, then the Keep Alive interval will not matter.  The reset invalidates an existing connection and you are Out until you reconnect. 

A reconnection, of course, has no context for whatever was happening before.

If that is it, then getting someone to troubleshoot the network is probably the best answer.

RLF