The $ACM service provides a common interface to all functions
    supported by the Authentication and Credentials Management (ACM)
    authority. The caller must specify the function code and any
    applicable function modifiers and item codes for the requested
    operation.

    The $ACM service completes asynchronously; for synchronous
    completion, use the $ACMW form of the service.

    Format

      SYS$ACMW  [efn], func, [context], itmlst, acmsb, [astadr],

                [astprm]

    C Prototype

      int sys$acmw  (unsigned int efn, unsigned int func, struct

                    _acmecb *context, void *itmlst, struct _acmesb

                    *acmsb, void (*astadr)(__unknown_params), int

                    astprm);

1 - Description

    Beginning in OpenVMS Version 7.3-2, a number of functional
    changes were made to SYS$ACM[W]. In the following descriptions
    of these changes, nonprivileged processes refer to processes
    running in user mode that do not have SECURITY privilege.

    These changes are the following:

    o  Timeout processing

       Timeout processing is now enforced for nonprivileged
       processes. Othe processes can request time processing by
       specifying the ACME$M_TIMEOUT function modifier.

    o  Dialogue mode iteration limit

       Nonprivileged processes are now limited in the number of
       iterative requests they can make in a dialogue sequence of
       calls.