JCL Reference: http://www-01.ibm.com/support/docview.wss?uid=pub1sa22759715
JCL User's Guide: http://www-01.ibm.com/support/docview.wss?uid=pub1sa22759807
You'll have to click on the link on each page to get to the actual manual. These are the release 1.13 versions of the manuals -- if you're not using 1.13 z/OS yet, then some parts of these manuals may not apply.