Object files can contain global constant values. An object
    file used with SDA typically contains symbol definitions for
    data structure fields. Such an object file can be generated by
    compiling a MACRO-32 source module that invokes specific macros.
    The macros, which are typically defined in SYS$LIBRARY:LIB.MLB
    or STARLET.MLB, define symbols that correspond to data structure
    field offsets. The macro $UCBDEF, for example, defines offsets
    for fields within a unit control block (UCB). OpenVMS Alpha
    and Integrity servers provide several such object modules in
    SDA$READ_DIR, as listed in the following table. For compatibility
    with OpenVMS VAX, the modules' file types have been renamed to
    .STB.

    File                      Contents

    DCLDEF.STB                Symbols for the DCL interpreter
    DECDTMDEF.STB             Symbols for transaction processing
    GLXDEF.STB                Symbols for OpenVMS Galaxy data
                              structures
    IMGDEF.STB                Symbols for the image activator
    IODEF.STB                 I/O database structure symbols
    NETDEF.STB                Symbols for DECnet data structures
    REQSYSDEF.STB             Required symbols for SDA
    RMSDEF.STB                Symbols that define RMS internal and
                              user data structures and RMS$_xxx
                              completion codes
    SCSDEF.STB                Symbols that define data structures for
                              system communications services
    SYSDEF.STB                Symbols that define system data
                              structures, including the I/O database
    TCPIP$NET_GLOBALS.STB*    Data structure definitions for TCP/IP
                              internet driver, execlet, and ACP data
                              structures
    TCPIP$NFS_GLOBALS.STB*    Data structure definitions for TCP/IP
                              NFS server
    TCPIP$PROXY_GLOBALS.STB*  Data structure definitions for TCP/IP
                              proxy execlet
    TCPIP$PWIP_GLOBALS.STB*   Data structure definitions for TCP/IP
                              PWIP driver, and ACP data structures
    TCPIP$TN_GLOBALS.STB*     Data structure definitions for TCP/IP
                              TELNET/RLOGIN server driver data
                              structures

    * The TCPIP$*.STB files are available only if TCP/IP has been
    installed. These files are found in SYS$SYSTEM, so that all files
    are not automatically read in when you issue a READ/EXEC command.