The XCS network is based on the use of shared resources by connected processors. Disruptions in the ability of the sharers to cooperate therefore represent a serious restriction to the functionality of XCS. If non-redundant connections fail, the MSCF connection must be reestablished quickly or the processor disconnected, so that the XCS network can continue to operate unhindered.
Since network entry and exit require an intact XCS configuration, all outstanding join and leave reconfigurations are aborted if a connection is lost between two XCS sharers. The processors entering and leaving the network disconnect from the MSCF network and terminate MSCF.
Crash detection and fail reconfigurations are only possible if the target configuration is error free.
If a connection is lost between two active XCS sharers, automatic disconnection from the XCS network is not always acceptable. The system behavior can therefore be controlled by MSCF configuration parameters RECOVERY-START (see "Global control parameters").
Automatic error recovery (RECOVERY-START=*AUTOMATIC / *SECURE)
If the MSCF connection between two active processors in the XCS network fails, the one with the higher value for HOST-PRIORITY in the configuration file disconnects from the network. If both these processors have the same value, the one that entered the network later disconnects from it.
Operator decision
The failure of an MSCF connection between two processors is announced on the consoles of both processors by the question MCS1101. The question can only be answered indirectly by carrying out one of the measures cited in the message text. Systems support can do the following:
Eliminate the cause of the connection failure or provide a new path and then reestablish the MSCF connection via the START-MSCF-CONNECTION command.
Disconnect one of the XCS sharers affected by the loss of connection via the command STOP-SUBSYSTEM MSCF,SUBSYSTEM-PARAMETER='FORCED=YES'.
The fault remains until the MSCF connection is reestablished or one of the two processors disconnects from the XCS network.