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Removing time series from Database

Please note that just deleting data from the timeSeriesTable could have adverse effects. Directly editing the database is always a last effort. So indeed make sure to make a backup first!

It is indeed also possible to remove data from the database manually. But to start: best approach would be to be able to just start with an empty database and import and process the data that you really need. The configuration should have been set-up to allow this.

If this is not feasible and you have a localDatastore with data that is difficult to reproduce, it is indeed possible to delete data using DBVisualizer. In my experience it is not that difficult. First you need to make a connection as described here:
HOW-TO connect to a localdatastore with DBVisualizer
(make sure FEWS is not running). Then use SQL to query the data you want to have removed. Can be simple:

DELETE FROM TimeSeries WHERE moduleInstanceId='some moduleinstance'

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But you You can use SQL to further refine what you want.

So far so good, but this NOTE: This just clears the data from the database, but not reduce disc space. To do this, start FEWS, press F12 and select under Database the option "repair and defrag local database". This will reduce the file size.
Please note that just deleting data from the timeSeriesTable could have adverse effects. Directly editing the database is always a last effort. So indeed make sure to make a backup first!