IOS_PORT_SPEED

Description:

Reports if any FICON® links are operating at a speed that is less than the maximum capable speed of the ports on each side of the link. The term link refers to the connection between two FICON ports. In a switched point-to-point topology, there is a link between the channel and the entry switch port, and a link between the exit switch port and the control unit port. In a point-to-point topology, there is a single link between the channel and control unit port.

During link initialization, the ports on each side of the link negotiate the operating speed of the link. Ideally, the operating speed of the link is the highest capable speed that is common between the two ports. For example, if an 8 Gbps port is connected to a 16 Gbps port, the link would ideally operate at 8 Gbps. However, if excessive errors occur during link negotiation due to the quality of the link (as might be caused by dirt or dust on the optics, or damaged cables), the link negotiates at a lower speed. This can result in increased I/O latency and reduced throughput.

Note: The ports on both sides of the link must support the Fibre Channel Read Diagnostic Parameters (RDP) extended link service and must both provide their maximum capable and operating speeds in order for this check to perform its function. Otherwise, the system cannot determine whether an exception exists. This might require the installation of a certain level of switch or control unit firmware. Contact your switch or control unit manufacturer to determine the required hardware and firmware levels to support this function.

The system runs this check when any of the following events occur:

IBM® Health Checker for z/OS® starts.
A channel path becomes available or is varied online and the system detects that the port speed is less than the maximum capable speed.

The information in the report includes the identifiers for the two ports on the link, their maximum capable speeds, and the negotiated or operating speed of the link.

Reason for check:

Port (link) speed is directly related to I/O latency and throughput. By monitoring this value, this health check can provide insight into fabric problems, such as hardware errors, I/O misconfiguration, or congestion.

z/OS releases the check applies to:

z/OS V2R1 and later, with APAR OA49089 and supporting processor, DASD, and switch hardware.

Parameters accepted:

None.

User override of IBM values:

The following sample shows the defaults for customizable values for this check. Use this sample to make permanent check customizations in an HZSPRMxx parmlib member used at IBM Health Checker for z/OS startup. If you just want a one-time only update to the check defaults, omit the first line (ADDREPLACE POLICY) and use the UPDATE statement on a MODIFY hzsproc command. Note that using non-POLICY UPDATEs in HZSPRMxx can lead to unexpected results and is therefore not recommended. End of change

ADDREPLACE POLICY[(policyname)] [STATEMENT(name)]
UPDATE
CHECK(IBMIOS,IOS_PORT_SPEED)
ACTIVE
VERBOSE(NO)
INTERVAL(ONETIME)
SEVERITY(MED)
DATE('date_of_the_change')
REASON('Your reason for making the update')

Debug support:

No.

Verbose support:

No.

Reference:

For more information about diagnosing fiber optic link problems, consult the documentation supplied by your hardware vendor.

The DISPLAY M=DEV command with the LINKINFO parameter also provides the operating and capable speeds of the port for a device path, as well as other information. For more information, see z/OS MVS System Commands.

Messages:

This check issues the following exception messages:

IOSHC151E

See IOSHC messages in z/OS MVS System Messages, Vol 9 (IGF-IWM).

SECLABEL recommended for MLS users:

SYSLOW