With ISPF you can define additional files for the ISPF libraries, such as ISPPLIB, ISPMLIB using the LIBDEF command.
You can display the current LIBDEFS using the ISPLIBD command. I remember this name because it is ISP for ISPf …. LIBraray Display – so ISPLIBD.
If you want to see what data sets are allocated use the TSO ISRDDN command.