Configuration Guide User Manual

Micro-PWC CONFIGURATION GUIDE
Historical Database 231
•4 weeks
•8 weeks
• 16 weeks
Click the desired entry to select it; it will be highlighted. If a retention time other than Infinity is selected, the
data is stored in a circular buffer. If Infinity is selected, data will be retained until the Number Retained
specification is exceeded. When the time interval exceeds that which has been configured, the oldest data
will be overwritten by new data. The amount of available disk space and the number, frequency and reten-
tion rate of other collections on the system should be considered carefully when configuring the retention
time. The default time interval is eight hours.
5.2.3.1.2 Number Retained Option
To configure the number of collections to be retained for the selected historical tag, use the Number
Retained list box, which contains the available options:
• Infinity
•10
•50
•100
•500
•1,000
•5,000
• 10,000
• 50,000
• 100,000
• 500,000
• 1,000,000
Click the desired choice to select it. The default selection is Infinity, in which case data will be retained until
the Retention Time is exceeded. The amount of available disk space and the number, frequency and
retention rate of other collections on the system should be considered carefully when configuring the num-
ber of collections to be retained.
✎ Note If both a time interval and a number of samples (refer to Section
5.2.3.1.2, Number Retained Option) are configured, the first one to
be completed will be used as the retention limit. For example, if
both a time interval of one hour and 100 samples are configured for
a retention span, and only 60 samples per hour are collected, then
the 61st sample will overwrite the oldest sample stored.
✎ Note If both a time interval ( sec ) and a number of samples are
configured, the first one to be completed will be used as the
retention limit. For example, if both a time interval of 1 hour and 100
samples are configured for a retention span, and only 60 samples
per hour are collected, then the 61st sample will overwrite the
oldest sample in the circular buffer.