How does DataMiner manage the real time trending info stored in the real time trending database tables. For a DMA with real time trending window set to say the default 24 hours, does DM periodically delete all table data older than 24 hours and therefor only contain data records for the past 24 hours? This appears not to be the case. When inspecting that actual MySQL RT trending tables I see data entries that go back many months.
Thanks
Hi Jeff,
It depends on the Database.
For MySQL we will indeed periodically check the table and delete all records that are older than the specified time using a DELETE query.
For cassandra we use the built in mechanism called TTL (time to live), when we write a trendrecord to the cassandra table, we tell cassandra how long this record should be kept alive. Once the time has expired the record is automatically deleted.
I suspect in your case where the RT table goes back for months, there might be an issue with the delete query timing out. This should be logged in the logfiles.
With MySQL, the driver could also have the databaseOptions=”partitionedTrending” specified. Trending is then added to partitions and these get dropped one by one instead of a delete query that needs to iterate over the entire table every time.