invo_handle

    OpenVMS usage:invo_handle
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value

    Handle for the invocation to be updated.

 invo_context

    OpenVMS usage:invo_context_blk
    type:         structure
    access:       read only
    mechanism:    by reference

    Address of an invocation context block that contains the values
    to be written to the registers.

    Each register that is set in the invo_mask parameter is updated
    using the value found in the corresponding IREG or FREG field of
    the invocation context block. The program counter and processor
    status of the given invocation can also be updated in this way.
    No other fields of the invocation context block are used.

 invo_mask

    OpenVMS usage:mask_quadword
    type:         quadword (unsigned)
    access:       read only
    mechanism:    by reference

    Address of a 64-bit vector, where each bit corresponds to a
    register field in the passed invo_context. Bits 0 through 29
    correspond to IREG[0] through IREG[29], bit 30 corresponds
    to STACK_POINTER and cannot be changed, bit 31 corresponds to
    PROGRAM_COUNTER, bits 32 through 62 correspond to FREG[0] through
    FREG[30], and bit 63 corresponds to PROCESSOR_STATUS.