Product specifications

Accessing 800xA via OLE DB
476 3BDS011222-510 B
7. If you choose a raw reading the default number of max item returned is 0,
which means that you will get all values in the log. You can limit this by putting
a number in this field.
8. If you choose a processed reading you have more options. You can choose what
kind of calculation you want to perform on the data.
This by changing the calculation field with help of the list. Observe that all
OPCHDA servers may not support all type of calculations.
9. After this you have an option to give the number of returned values, Item
Return Count, or Resample Interval. When you give the resample rate you
give the time in seconds between samples.
10. Click Apply to verify the changes.
Example Command Line
As you could see in the section about the command line the fourth way of giving the
command line included the ITEMID keyword. This alternative has best performance
of the four. If you use the ITEMID keyword the command line can look like this:
GET_HISTORY(ITEMID={5D941E07-AD9F-40B8-9CBD-
4FDDC15BFF3C}{2EAB2220-77C0-46EE-BECB-
1C0D6DE0989B}:VALUE,OPC_5s_5h; FROM=HOUR; TO=NOW)
In the third case of GET_HISTORY you can give the GUIDs or path and /or names
of the Objects and Aspects. The difference between them is also the performance,
i.e. how long time it takes to find the specific object or aspect. If you use the GUIDs
for both the OBJECT and the ASPECT, which is the fastest way after using
ITEMID, the command line can look like this:
GET_HISTORY(OBJECT={5D941E07-AD9F-40B8-9CBD-4FDDC15BFF3C};
ASPECT={2EAB2220-77C0-46EE-BECB-1C0D6DE0989B};
PROPERTY=VALUE; LOG=OPC_5s_5h; FROM=HOUR; TO=NOW)
If you do not want to use the GUIDs you can give the path to the object and just the
name of the aspect. You can choose to use either “/” or “.” in the path as shown
below.