SDA obtains its information from the following:

    o  Images (.EXE files)

    o  Image symbol table files (.STB files)

    o  Object files

    SDA also defines symbols to access registers and to access common
    data structures.

    The only images with symbols are shareable images and executive
    images. These images contain only universal symbols, such as
    constants and addresses.

    The image symbol table files are produced by the linker with the
    /SYMBOLS qualifier. These files normally contain only universal
    symbols, as do the executable images. However, if the SYMBOL_
    TABLE=GLOBALS linker option is specified, the .STB file also
    contains all global symbols defined in the image. See the OpenVMS
    Linker Utility Manual for more information.

    Symbols can include lowercase letters. Commands that manipulate
    symbols (such as DEFINE, SHOW SYMBOL, and UNDEFINE) require these
    symbols to be enclosed within quotation marks ("symbol" ).

    Some SDA commands predefine additional symbols. This includes
    SET CPU and SET PROCESS (as shown in the following subtopics) and
    also SHOW DEVICE and SHOW CLUSTER.