title: How do RDBMS deal with stale connections?
body: <p>Consider setting up a connection to a RDBMS, then yanking the network plug. (You'll get the 
  same effect if the connection goes through a NAT gateway, and the gateway decides to purge that connection.)</p>
  
  <p>At that point the RDBMS server is waiting for a query, or whatever, which will never occur. And the TCP connection won't be closed by tha client since that's not on that network anymore. Presumably the server will not close it either since it still believes the connection to be open.</p>
  
  <p>Do typical RDBMS handle this with timeouts and/or  implementing a simple keepalive mechanism over TCP ? Anyone have any experience with this for Oracle,SQL Server and MySQL ?</p>
  
  <p>Edit; More digging suggests mysql purges connections after 8 hours of inactivity.</p>