I would like to write a health check for z/OS but am unclear on where to begin. Any advice, examples, or direction available?
Also, is it possible to write a Health Check in Unix System Services?
So, first, start with IBM Health Check for z/OS User's Guide. It will point you to some samples in SYS1.SAMPLIB you can use as a base. Specifically, start here.
As to your question about writing a Health Check under Unix System Services, it depends on what you want to do. Purely under USS, no. In order to have a Health Check, you need to register with the Health Check address space, and report status to it in a specific way. So the Health Check needs to be written in Metal C, assembler, or System REXX. (I'd recommend System REXX unless you're fluent in Metal C or assembler.) And you'll need a z/OS system programmer to install the check to a system library.
However, as documented in the System REXX reference, you can invoke USS services from with System REXX, and I believe Metal C and assembler as well, so depending on what you're trying to do, you may be able to write the Health Check you're trying to write.