"Coverage" column in PRTG
When viewing live graphs or reports in PRTG, there is a special column "Coverage". This value tells you if the monitoring was actually working all the time and whether it has covered the complete time period.
E.g. if PRTG is shut down for 15 minutes of an hour you will see a value of 75% of coverage for this hour (for the remaining 45 minutes) that were actually covered by monitoring.
If you need reliable and complete data from your monitoring this value should always be 100% or close to 100%.
Coverage below 100%
If the coverage is below 100% but PRTG was running all the time then there may be a technical problem with the sensor. PRTG was not able to get all the data it needs to completely calculate the traffic over time. Most common reasons are network problems (e.g. packet loss, connectivity issues) and device problems (e.g. some devices limit the number of SNMP request per minute, so if they are scanned too frequently a number of requests remain unanswered).
If you are experiencing problems with SNMP sensors, a 'High Compatibility' setting may help. Please see Why do I see huge peaks or spikes in graphs for SNMP sensors? for more details.
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