The serial port design on the p5 Servers requires special considerations when used for other applications while an HMC is attached. This technote describes these considerations.
On the p5 servers, you cannot use any of the serial ports for TTYs or for heartbeats as you could on previous pSeries servers. The two ports on the machine go to the service processor. The ports on the host partition are virtual ports, and this is only when the Hardware Management Console (HMC) is not managing the machine. The SP controls the serial ports.
The serial ports S1 and S2, at the rear of the system, are only available if the system is not managed using a HMC. In this case, the S1 and S2 ports support the attachment of the serial console and modem. If an HMC is connected, a virtual serial console is provided by the HMC (logical device vsa0 under AIX visible with the lsdev -l vsa0 command). When the HMC is connected, the S1 and S2 ports are not usable by applications, such as for an HACMP heartbeat.
If additional serial port functionality is needed, optional PCI adapters are available (PCI 8-port adapter FC 2943 or PCI 128-port adapter FC 2944).
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