Planning and operation considerations

Guidelines for planning and operating in a dynamic I/O environment are detailed in the appropriate z/OS®, and z/VM® publications. The planning and operation considerations described in this section are additional guidelines that apply to a dynamic I/O environment.

You should plan carefully to avoid confusion when moving CHPIDs and eliminate duplicate device situations should a backout be required when a power-on reset is performed.

• Prepare for a backout situation.

  Before changing the currently active I/O configuration, prepare for a possible backout situation. Record the current CHPID assignments and the planned I/O changes.

  It is important to prepare for a backout situation. A backout situation occurs when changes are made to the I/O configuration but the changes are not saved prior to performing a power-on reset. If the changes are not saved, the CHPID assignments prior to the first dynamic I/O change takes effect.

  In addition CHPID assignments after a backout will also reflect any changes made by hardware operator tasks or control program commands.

• Avoid CHPID reconfigurations concurrent with dynamic I/O changes

  Do not perform hardware operator tasks and system control program commands to cause a CHPID to be moved from one LP to another or to give or take access to a shared channel path while dynamic I/O changes are being made. Use these commands only after dynamic I/O changes are saved.