Prior to z/OS® V2R1, there were no IBM® Health Checker for z/OS related system parameters in IEASYSxx. Now, with z/OS V2R1, for example, there are two system parameters, HZS and HZSPROC. You'll encounter these as you do the Steps for optimizing IBM Health Checker for z/OS.

So, what happens if you share IEASYSxx parmlib members in a sysplex with systems that are at different levels? You can make this work using the WARNUND system parameter, which tells the system to issue message IEA660I when it encounters unsupported IEASYSxx statements are encountered, rather than stopping an IPL to prompt for a correct statement. That means that a system can use an IEASYSxx member that includes statements that are not supported on the system's release level, simply ignoring the ones the system does not support. The system issues message IEA660I for IEASYSxx statements that the system does not support.

To use the WARNUND statement in IEASYSxx see the Overview of IEASYSxx parameters in z/OS MVS Initialization and Tuning Reference.