User Manual

Operating Reference
Trends
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Offline Trendlog Objects
Offline trend data can be recorded and saved by Trendlog objects within the
automation and control system even when the management station is not
connected. The recorded data can then be saved in the trend database. Offline
trend data can be retrieved and displayed in the trends.
Online Trendlog Objects
Data recorded by online trending and saved to the trend database (for example,
using save continuously) can be retrieved and displayed in the trends. Online
Trendlog objects record data also when the Trend View is closed.
Database Storage Capacity
In the database, 10 GB is saved for the SQL Server Express and 250 GB of
historical data for SQL-Server. Once 90% of the database size is reached, 10% of
the oldest data entries are deleted. This 10% of data always refers to the entire
time axis for the collected data. Therefore, it cannot be exactly determined how
many entries or the database size that is actually deleted. Additional incoming
entries are rejected if the 10% of data entries cannot be deleted before reaching
98% of the database size.
The data amount is comprised of the following:
● System activities
● Alarm messages
● Trend data
Change to Daylight Savings Time
● Date and time data is saved in UTC format. Entries are in double for one hour
when setting back to normal time. In this case, the curve displays using both
values. When switching to daylight savings time, no value displays in this hour
and the displayed line is straight between the two measured values.
● A system message Anomaly is generated when changing times that must be
acknowledged.
10
0
10 GB
90% of DB
# =10%
Time
GB
98% of DB
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