Vendors tend to change the URLs for the publicly available manuals frequently. To find a specific manual that is generally available to the public, use your favorite search engine with your specific keyword search.

For instance Type ‘IBM DB2 V11 Documentation’ in your search field to find the guide on the IBM website. Here are the top results I received on this day.

IBM DB2 for z/OS Product Documentation - United States
It is a one-stop shop for all IBM product documentation, and it provides an IBM-wide view ... DB2 Utilities Suite for z/OS, V11, Program Directory
โ€ŽNew! IBM Knowledge Center ยท โ€ŽAre you new to DB2 for z/OS?
DB2 11 for z/OS documentation - IBM
Welcome to the IBM DB2 11 for z/OS documentation, where you can find topics that you need to useDB2 for z/OS. By using this information, you can install or ...
IBM DB2 for z/OS - DB2 11 for z/OS
IBM DB2 for z/OS helps you to reduce cost and complexity in your IT infrastructure, simplify compliance, and leverage your core asset โ€” your data.