On Alpha and Integrity server systems, allows an OpenVMS thread
    to assume the identity of another persona.

    Format

      SYS$PERSONA_ASSUME  persona ,[flags], [previous], [acmode]

    C Prototype

      int sys$persona_assume  (unsigned int *persona, unsigned int

                              flags, unsigned int *previous, unsigned

                              int acmode);

1 - Arguments

 persona

    OpenVMS usage:persona
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference
    Address of a longword in which the persona identification handle
    is expected.

    If the value passed is ISS$C_ID_NATURAL, then the state of the
    calling thread is returned to the natural persona.

 flags

    OpenVMS usage:mask_longword
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Ignored.

 previous

    OpenVMS usage:persona
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference
    Address of a longword into which the persona identification
    handle of the currently active persona being replaced is written.

 acmode

    OpenVMS usage:access_mode
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Access mode to be considered when assuming a persona. The acmode
    argument is a longword containing the access mode.

    The most privileged access mode used is the access mode of the
    caller. Only equal or more privileged access modes can use this
    persona.