I worked with mainframes long ago, for about a year. When it came to JCL, the advice I got and what everyone I worked with did, was to copy working JCL and mod

I worked with mainframes long ago, for about a year. When it came to JCL, the advice I got and what everyone I worked with did, was to copy working JCL and modify it. I never wrote it from scratch, nor did I know anyone who did.