we use the PI Interface for RDBMS to read data from an Oracle database.
We use the standard way of reading the latest values by using the TS parameter as described in the manual. Scan rate is 5 minutes.
The exdesc attribute for each tag is configured like this:
The SQL statement looks like this:
SELECT TIME_STAMP, VALUE, 0 FROM PE_HISDATA WHERE TARGETNAME = ? AND TIME_STAMP > ? ORDER BY TIME_STAMP ASC;
All values will be read, but the I/O rate will increase linearly and we can also see that the amount of archived events from this interface increases linearly.
Events archived per second:
If the interface is restarted, the I/O rate will start from zero again, but we will have the same behavior over time as described above.
Obviously the TS parameter does not work as expected, but rather is set to the start time of the interface and for each scan the interface will read from the start time of the interface instead of from the time of the last scan.