I found this behaviour at a customer: following a new release of their website, the OOTB "Visits by Landing Page" started bloating up (twice as many measurements), becoming the #1 contributor to measures.
Since this coincides exactly with the new website release, my thought is that if the Landing Pages names have changed even a little bit, they will get separate splittings thus resulting in 'duplicate' buckets for data. But is this assumption correct?
(Yellow line is the aforementioned BT, the point it starts rising is the morning of the new release)
Check the configuration for that business transaction (the splitting options in particular), I looked at mine and by default it is only looking at the top 50 most frequent, perhaps you have a different configuration there that's leading to that behavior.
Yep, that'll do it. Reset those to default or whatever option you prefer. If you have the auto cleanup running it should clear out all of those excessive splittings once they haven't been updated for a while.
You can check your tasks and monitors in the cockpit to make sure that it's running (it should be by default) on a set schedule in the evenings. Then to make sure it's purging old non-updated data go to server settings -> PW and in the storage management tab make sure the auto-purge option is selected. We had measures from an old misconfigured BT sitting in the PW, then enabling this it will start to remove these during the clean up process. If it's a lot it will take a number of runs before they are gone. In our case it was before the 50,000 splitting hard limit so there were millions of splittings in there. It's back down to a reasonable number now.
Thanks, James! We have a now-deleted BT with about 400K measures that's been here a while. I double-checked my settings to make certain that both the task and the auto purge are enabled - they are.
Let's hope that the process finally begins working!