loading symbols for a shared library

Hi All
I'm trying to load the symbols for a shared library located in a
separate file than a library itself. I do that as follows:
(gdb) symbol-file symbols.dbg
Reading symbols from symbols.dbg...done.

I get no errors while loading the library but when doing the "bt"
command it looks like the symbols have not been loaded.
"info sharedlibrary" shows that the symbols have not been loaded:
From      To        Syms Read   Shared Object Library
0x<ADDR>  0x<ADDR>  Yes (*)     /path/library.so.1
(*): Shared library is missing debugging information.

I use GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2) 7.7.1.

Please write me how can I load the symbols properly or how can I
diagnose my issue.

thanks for help