Enterprise Test Server provides extensions to several MVS features. These extensions can be added to existing source and can remain there since they are treated as comments by the host operating system.
You write the extensions as comments, so that if you move your JCL or IDCAMS back to the mainframe they are ignored. The start of the Enterprise Test Server extensions within a comment is indicated by the four-character string “MFE:”. Extensions are identified by keywords. These keywords begin with the % sign, to avoid any possible conflict with z/OS keywords.
There is no change to standard JCL or IDCAMS comments.