System managers can receive notification of a change to the
    system parameter file by setting up an access control list (ACL)
    on the file to signal such an event, as in the following example:

    $ SET SECURITY/ACL=(ALARM=SECURITY,ACCESS=WRITE+FAILURE+SUCCESS)-
    _$ SYS$SYSTEM:X86_64VMSSYS.PAR

    For more information about setting ACLs, refer to the VSI OpenVMS
    User's Manual and the VSI OpenVMS Guide to System Security.

    Both the WRITE ACTIVE and WRITE CURRENT commands send a message
    to OPCOM and log the event. The audit log also provides a list of
    the changed parameters along with their old and new values.