These are, indeed, procedures in various libraries written to allow COBOL programs to access some Guardian features not available via standard COBOL statements.
All of the NonStop manuals can be found by first going to:
http://www.hp.com/go/nonstop-docs
On that page, scroll down to the heading "NonStop Technical Library".
Under that heading, click on the link that includes your system type: H-series, J-series, or G-series. The page that leads to lists all of the manuals for the given system type. A lot of the manuals are the same for all three system types, but a few do differ.
The manuals are listed alphabetically by title. The product name often is not at the beginning of the title, so you might have to use your web browser's search in page function to look for the product name. In a few cases, the product name is not in the title at all. For example, "Guardian Disk and Tape Utilities Reference Manual" covers BACKUP, RESTORE, DSAP, DCOM, PAK, and UNPAK, BACKCOPY, and tape DEFINEs, none of which appear in the title. In cases where you cannot find the product name in the titles, using the search box at the top of the page often can help. Also you can try a Google search for the product name, restricting the search to HP's sites by including site:
hp.com in the Google search box.
The manual title is a link to a .pdf file that contains the entire manual. For large manuals, it can be a little awkward to navigate within the manual, but the table of contents and index of a lot of the manuals have live links to the part of the manual indicated, which can help. The chapter titles down the left side of the Adobe Reader window usually are fairly descriptive of the contents of the chapter, but some old manuals just use names like TPCONTNT, TPSEC01, TPINDEX, etc. and you just have to navigate them as best you can.
It is possible to save the .pdf file for a manual on your PC, so for manuals you expect to consult a lot, that can save you a lot of time accessing the HP web site. Either use the Save function on screen after you have opened the manual, or right-click on the document title and choose Save Target As from the page that lists all the manual titles.