ExDesc (extended descriptor)
- Last UpdatedNov 22, 2022
- 2 minute read
- PI System
- PI Interface for Ping 2.1.2.49
- Interfaces
The ExDesc attribute configures a variety of run-time settings, two of which are included in every interface and are described in the following table.
Note: Keywords must be specified in upper case.
Data size
Ping sends an ICMP echo request packet whose Data field is 56 bytes. To use a data size that is different from this number, specify the DATASIZE keyword. For example,
DATASIZE=20;
tells Ping to send an ICMP echo request packet that contains a Data field size of 28 bytes
Note: As indicated in the previous example, there is an 8 byte difference between the number indicated by DATASIZE= and the size of the Data field in the ICMP packet. The reason for this difference is because of backwards compatibility issues
Interface node with multiple IP addresses
A PI Interface node on which Ping runs may have multiple network interface cards, and hence, multiple IP addresses. Normally, these IP addresses are on separate networks; for example a machine may have addresses 192.168.10.100 as well as 208.242.148.10. The Windows operating system will use the appropriate network card for sending pings. For example, in order for the Interface to ping 192.168.10.101, Windows will use the network card with address 192.168.10.100. Likewise, in order for the Interface to ping 208.242.148.11, Windows will use the network card with address 208.242.148.10.
However, there may be instances where multiple IP addresses are on the same network; for example, a machine may have addresses 192.168.10.100 and 192.168.10.102. For such a situation, the user may explicitly specify an IP address that the Interface will use to ping the remote device. He indicates so via the OUTADDR keyword. For example
OUTADDR=192.168.10.100;
|
Keyword |
Description |
Example |
|---|---|---|
|
PERFORMANCE_POINT |
When set, such point stores the amount of time, in seconds, that it takes an interface to complete a scan for a particular scan class. The lower the scan time, the better the performance. |
PERFORMANCE_POINT For details, refer to the PI Universal Interface (UniInt) User Guide (https:// techsupport.osisoft.com/ Downloads/All-Downloads/All- Groups/All-Products/All- Categories/Current-Version/ uniint/) . |
|
TRIG or EVENT |
For event-driven input points: each time the specified point changes, the SQL query is executed. If the point name contains spaces, you must enclose it in single quotes. If there are subsequent parameters, you must specify a comma after the /EVENT specification. Valid conditions:
|
/EVENT = sinusoid, … or /EVENT = sinusoid anychange, … |
ExtendedDescriptor Length
Depending on the version of the PI API and the Data Archive, this interface supports an ExDesc attribute whose length is at most 80 or 1023 characters. The following table indicates the maximum length of this attribute for all the different combinations of PI API and Data Archive versions.
|
PI API |
Data Archive |
Maximum Length |
|---|---|---|
|
6.0.2 or later |
4.370.x or later |
1023 |
|
6.0.2 or later |
Earlier than 3.4.370.x |
80 |
|
Earlier than 1.6.0.2 |
4.370.x or later |
80 |
|
Earlier than 1.6.0.2 |
Earlier than 3.4.370.x |
80 |
Performance Points
For UniInt-based interfaces, the extended descriptor is checked for the string PERFORMANCE_POINT. If this character string is found, UniInt treats this point as a performance point.