DCL_CTLFLAGS is a bit mask that alters default behavior for
    certain DCL-related functions on a systemwide basis. However,
    the default values satisfy the needs of most systems.

    Bits 0 and 2 control the formulation of system-generated process
    names for processes created using the SPAWN command or LIB$SPAWN
    library routine. They are provided for compatibility with
    behavior of prior OpenVMS versions. Note that you can eliminate
    the use of system-generated names by supplying your own process
    names.

    Bit 1 controls the token size used by DCL.

    Bit 3 controls the maximum number input parameters to command
    procedure.

    Bit 4 controls the the maximum length for an user name, for which
    OpenVMS mail forwarding address is set.

    DCL_CTLFLAGS bits are described in the following table.

    Bit   Description

    Bit   If clear (the default), the numeric portion of a system-
    0     generated spawned process name is generated randomly. If
          set, the numeric portion is generated sequentially starting
          with sequence number 1.

          The option of sequential generation is provided for
          compatibility with OpenVMS versions prior to Version
          7.3-1. However, this choice can be very expensive in
          performance terms because of the mechanism for finding
          the next available process name. This mechanism attempts to
          create all process names beginning with sequence number 1
          until it finds one that is unused.

          Random generation is the preferred choice because it
          results in a very high probability of finding a unique
          name on the first try.

    Bit   Controls the token size used by DCL. If clear (the
    1     default), this bit instructs DCL to use the traditional
          token size. A token cannot exceed 255 characters. If this
          bit is set, extended tokens are used. Extended tokens are
          4000 characters.

          Note that if you turn on extended tokens, file
          specifications can exceed 255 characters, which might
          require larger structures for parsing file specifications.

    Bit   If clear (the default), the numeric portion of a system-
    2     generated spawned process name has a maximum value of
          65535. If set, the numeric portion of the name has a
          maximum value of 255.

          The option of a maximum of 255 is provided for
          compatibility with OpenVMS versions prior to Version 8.3,
          when it was the only choice. The larger maximum allows many
          more unique spawned process names for a given process.
          For this reason, it is the preferred choice. However,
          the larger maximum uses two additional characters from
          the process name, which might make it more difficult to
          identify users uniquely by looking at their spawned process
          names. If this is an issue on your system, setting bit 2
          might be a better choice.

    Bit   If clear (the default), command procedure supports the
    3     default eight optional parameters (that is, (P1,P2,...P8)).
          If set, command procedure supports up to sixteen optional
          parameters (that is, (P1,P2,...P16)). This is also
          applicable when using the CALL command to transfer control
          to a subroutine.

    Bit   This bit controls the the maximum length for an user name,
    4     for which OpenVMS mail forwarding address is set. If clear
          (the default), user name string length is set to a maximum
          length of 31 characters. If set, user name string length is
          set to a maximum of 255 characters.

          Note: Once this bit is set, user name length is set to
          maximum of 255 characters. Even if this bit is cleared,
          the behavior remains unchanged, that is, supports user name
          length of 255 characters, but there is no way to reset it
          to 31 characters.