Switch Operations Facility › SOF Server Configuration and Start-up › Define Switches

Define Switches

Normally, the SOF server automatically discovers all switches in the I/O configuration. There may be situations where the SOF server is not able to identify a switch, or may identify a switch improperly. Those situations will result in SOF being unable to properly correlate the switch among the multiple z/OS systems.

Those situations require adding a DEFINE SWITCH command in the INITCMDS file to do the following:

• Identify the switch to the local SOF server

  On a DEFINE SWITCH command specify the logical device number of the switch (as specified in the IODF of the local system) to identify the switch to the local SOF server. If this number is different on different systems in the SOF complex, then a different DEFINE SWITCH command will have to be directed to each different system. That can be done either by using IFSYS statements in a shared INITCMDS file, or by using a different INITCMDS file for each different system.

• Specify a DEVID for the switch that SOF will use to correlate the switch among the multiple z/OS systems

  On each DEFINE SWITCH command issued for the same switch, specify the same arbitrary DEVID. This lets SOF know which local switches to correlate globally as the same switch on multiple z/OS systems in the SOF complex. DEVIDs are further discussed in subsection Hardware Device IDs in section SOF Command Interface.

The DEFINE SWITCH command syntax is described in subsection Miscellaneous Commands in section SOF server Commands.

Use DEFINE SWITCH command in the following situations:

• A switch is not defined to a z/OS system in the SOF complex. This means the switch has no device number and no UCB as an I/O device.
• A switch is sometimes OFFLINE to a z/OS system in the SOF complex.
• A single physical switch is partitioned as multiple logical switches, and each logical switch presents the same serial number to a z/OS system in the SOF complex.

For any switch, as long as there is a UCB for the switch on at least one z/OS system in the SOF complex and the switch is online to that system, all SOF connectivity control commands directed to the switch will function normally.

Example: Switch between Systems

In a two-system SOF complex, a switch defined as logical device number 0001 in the IODF for SYSTEMA is defined as logical switch number 0002 in the IODF for SYSTEMB, and the switch is not defined to z/OS on SYSTEMB.

The following commands in a shared INITCMDS file would enable SOF to correlate the switch between systems:

IFSYS SYSTEMA
  DEFINE SWITCH 0001 009032.005.IBM.02.FAKESERIAL03.0000
ENDSYS
IFSYS SYSTEMB
  DEFINE SWITCH 0002 009032.005.IBM.02.FAKESERIAL03.0000
ENDSYS

Warning: After starting SOF for the first time, it is strongly recommended that you verify the switches as discovered by SOF in the shared I/O configuration, using SOF display commands or OPSVIEW option 3.5, to determine if DEFINE SWITCH commands may be required at your site.