CA Products Documentation is available in SupportOnline Home Page, choosing option 'Documentation' under tab 'Menu' , at the below URL Link 

https://docops.ca.com/home

In the search windows it is possible to locate for each CA Product the related set of Documentation Manuals sorted by the supported Releases.
How to retrieve from this same location the Documentation Guides of the old and unsupported Releases ? 
 

Z/OS - Mainframe Products 

This is possible selecting the light blue title:

Go to Bookshelves and PDFs to find documentation for previous releases.

posted under the search windows,

A new screen will be prompted in which it will be possible to type the CA Product name in the search window under the 'Search for Bookshelves and PDFs' section.
The new list obtained will show all the old Releases Guides still available for the selected product.