I am using Microsoft SQL v2 BETA with "Process data table" and "Difference" options switched on. I have two consecutive readouts from SQL like
| 20.01.16 19:49:28 | Id 3 | return 1537 [Int64] |
| 20.01.16 19:50:28 | Id 3 | return 1528 [Int64] |
I expect sensor to show "-9" value but it shows "4294967287". It seems to be a problem with presenting negative values.
What can I do to have this sensor work as I expect?
Article Comments
Quote from manual:
| Difference : The sensor calculates and shows the difference between the last and the current value returned from the data table. |
You need to assume that difference could be negativ... please be serious, this not amount of data traffic which obviously only increase but SQL query is for ANY kind of data which can eventualy be on the dark side of zero.
Jan, 2016 - Permalink
Hello Tomasz,
thank you for your reply.
I've received confirmation from our development that all counters within PRTG must be ever-increasing, they're built on a similar logic than we handle Delta Counters in our SNMP Delta-based Sensors which are ever-increasing. Supporting negative delta values would affect the current overflow handling and is not something we intend to change.
| The Counter32 type represents a non-negative integer which monotonically increases until it reaches a maximum value of 2^32-1 (4294967295 decimal), when it wraps around and starts increasing again from zero. |
| The Counter64 type represents a non-negative integer which monotonically increases until it reaches a maximum value of 2^64-1 (18446744073709551615 decimal), when it wraps around and starts increasing again from zero. |
Best Regards,
Jan, 2016 - Permalink
Hello Tomasz,
we appreciate your inquiry.
Delta sensors will never display negative values, that's not possible.
Counters(The information queried by delta sensors) are designed to be ever increasing, you got the result of 4294967287 because PRTG believes that the counter increased to a point were it did overflow (back to 0) and then increased up until 1528 again.
For Delta Counters/Sensors, the value must continuously increase and never decrease.
Best Regards,
Jan, 2016 - Permalink