Administration Guide

Selecting appropriate clocks for the SP Switch

The SP Switch2 does not require you to select switch clocks. This section applies only to the SP Switch. For the SP Switch, one of two switches in the system provides the master switch clock to the rest of the system. If the current master clock fails, or is removed from the configuration, the alternate master clock must be selected and the switch reinitialized.

The Eclock command establishes a master clock source after the system is powered up or when an alternate must be selected. It can set the appropriate clock input for every switch in the system or for a single switch after power on. After Eclock completes, the Estart command must be run.

Warning: Running Eclock after the switch is started may cause nodes to lose their clock source. Refer to Eclock in the PSSP: Command and Technical Reference for more information.

Selecting the SP Switch clock source

Using SMIT to set the SP Switch clock source:

TYPE

smit

• The System Management menu appears.

SELECT

RS/6000 SP Systems Management

• The RS/6000 SP Systems Management menu appears.

SELECT

RS/6000 SP Cluster Management

• The Cluster Management menu appears.

SELECT

Perform Switch Operations

• The Perform Switch Operations menu appears.

SELECT

Change/Show Switch Clock Source Settings

• The Change/Show Switch Clock Source Settings menu appears.

At this point, you can select options:

Figure 11. The Change/Show Switch Clock Source Settings (SP Switch only) SMIT menu

+--------------------------------------------------------------------------------+
|Change/Show Switch Clock Source Settings (SP Switch only)                       |
|                                                                                |
|&box. List Switch Clock Source Settings                                         |
|&box. Initialize Switch Clock Source Settings                                   |
|&box. Initialize Switch Clock Source Settings for a Switch                      |
|&box. Restore the Switch Clock Source Settings                                  |
|&box. Select Alternate Switch Clock Source Settings                             |
|&box. Create an Eclock Topology File                                            |
|&box. Automatic selection of Switch Clock Settings                              |
+--------------------------------------------------------------------------------+

When you choose a switch clock source setting option, you are prompted for a topology file name, and then the Eclock command is invoked.

The fastpath invocation for this menu is:

smit clock_src

Resetting the SP Switch clock

The SP Switch clock is synchronous across all nodes active on a switch. Its value is set to zero when the primary node powers on, and is later distributed by the Estart command to all nodes on or joining the switch. The switch clock will increase monotonically unless it is reset by one of the following events:

• The switch is powered off.
• An oscillator failure occurs on the switch board designated as the master clock source. (The switch designated as the master clock source provides the clocking signal for all other switch boards within the configuration.)
• The Eclock command is run.
• The Estart command is run while the oncoming primary node (or the primary node on High Performance Switch systems) is not active on the switch (for example, after the primary node is powered on).
• The Estart command is run after rc.switch or reboot has run on the primary node, but before the primary backup node has taken over. For further information, see Primary node takeover.

Note:

Select a new primary node that is active on the switch before the old primary node is powered off. This will prevent the switch clock from being reset to zero or to an indeterminate value on High Performance Switch systems. See Selecting the primary and primary backup nodes for more information on selecting a primary node.