Inbound packets from the network are placed into an OSA read buffer.  If all read buffers for an OSA-Express connection become full, it is likely that some packets after that will be dropped causing TCP data out of order and retransmit conditions as well as lost packets for other protocols such as UDP.  Prior to APAR PJ42415, the user had no way of knowing if or when they hit an all OSA read buffers full condition to know if that was the cause of any network disruptions they were encountering.  APAR PJ42415 created a new console warning message to let the user know if all the read buffers for an OSA-Express connection become full and alert the user that they might want to increase the number of OSA read buffers defined.

More information on APAR PJ42415 can be seen at the following link:

http://www-01.ibm.com/support/docview.wss?uid=swg1PJ42415

OSA-Express connections are defined to z/TPF production systems in pairs with one being the primary connection and the other the backup connection.  If the primary OSA-Express connection fails, the virtual IP addresses (VIPAs) associated with this OSA pair are moved to the backup OSA-Express connection in a non-disruptive manner such that the sockets using those VIPAs remain active.  Each OSA-Express connection also has one or two default gateway routers defined to it.  These gateways are used to route packets when the destination is not on this local network. 

Prior to APAR PJ42322, z/TPF would only monitor the status of gateways on the active OSA-Express connection over which traffic is currently flowing (the OSA-Express connection that currently owns VIPAs).  If there are problems with the gateways on the backup OSA-Express connection, the z/TPF operator would not be made aware of those problems until after the VIPAs were moved to the backup OSA-Express connection and traffic was unsuccessfully sent through those gateways.  If the primary OSA-Express connection failed causing the VIPAs to be moved to the backup OSA-Express connection, but the gateways on the backup OSA-Express connection were not working, this left the system with no network route and thus sockets failed.  APAR PJ42322 changed z/TPF to always monitor the gateways on a backup OSA-Express connection and inform the operator via new console messages if one or both default gateways fail. This allows you to take action and fix those gateways before they are needed.

More information on APAR PJ42322 can be seen at the following link:

http://www-01.ibm.com/support/docview.wss?uid=swg1PJ42322