User Manual

System overview
Data maintenance
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All parameter settings are non-volatile, that is, they are retained in the event of
a power failure.
Readback
All non-volatile PX process data and parameter settings can be read back into
XWP. However, parameter settings in the operator unit cannot be read back
into a tool.
Global parameter settings
Some parameter settings are identical in all automation stations, e.g., date and
time, calendar function blocks and Notification Class function blocks. To ensure
consistency, they are held in global objects which are automatically replicated
in the system.
Archived data
Setting parameters can be logged and archived. Archived data illustrates the
response of process or system variables or events over a time period, e.g., trend
data can be moved from the trend database into archive files. Archived data are
typically lists of one or more of the aforementioned variables and are preferably
stored and processed on the management level. Only small amounts of data are
archived at the automation level. Such data is normally forwarded to the
management level.
Ensuring consistency
Archived data only requires a consistency check in cases where it has been
moved from one application to another, e.g., from the automation level to the
management level. The data origin is not deleted until a check has been carried
out to ensure that the data has been transferred in full. This data is stored in
the non-volatile memory.
Irregularities in the logging of archived data are recorded in the data itself.
The life of the data is determined either by the user or by a configurable
application which automatically condenses or deletes this archived data.
Configuration and description data
Configuration and description data is data which is defined for a specific
system or project and only affects the appearance and response of the plant for
operation and monitoring purposes. Some configuration parameters are tool-
specific and control the options in XWP (e.g., connection allowed / not allowed,
etc.). Most configuration parameters, however, are mapped to BACnet and are
available to the clients. Typical data in this category is COV increment,
operating limits, access level, descriptive text, engineering unit, etc.
This data is defined during engineering and always originates in the tool itself.
Normally, the data is predefined with likely default values or even generated
automatically from the context. This data is static and cannot be modified
during operation. It is therefore not subject to consistency problems, and may
be duplicated elsewhere in the system to improve performance. If engineering
changes are made, you must ensure manually (through data import) that the
copies are identical to the original data in the engineering tool.
This data cannot be read back from the automation stations, and must
therefore be stored with the project data.
Metadata
Metadata is project-independent data from standard BACnet objects (e.g.,
analog input, schedule, etc.) which needs to be known by a tool or a client, e.g.,
texts for predefined BACnet enumeration, maximum size of arrays, data-type
information, fixed operating limits, etc. The metadata is loaded into the relevant
clients or tools at HQ and (except texts) cannot be modified after delivery. Text,
like the text for BACnet enumeration referred to above, must be localized
(language translation) and distributed to the clients and tools. This is part of
the localization process.