I have heard that Onestream supports ad-hoc queries and reporting. But I haven't yet found an easy way to send ad-hoc queries to our OneStream cubes. I'm searching for some sort of query interface like SQL, MDX, or DAX.
So far I've discovered that there is a REST API which allows me to retrieve data from an existing "cubeview". This is a helpful API for extracting data programmatically. But this certainly isn't considered "ad-hoc" since it requires that a cubeview be prepared and deployed in advance.
I had also seen that the REST API supports SQL statements but I have been warned against using those; since it circumvents the logical definitions of the cube, and these queries might become fragile and break over time (eg. after future upgrades to the onestream platform).
Besides those two options, what mechanism is available to send "ad-hoc" queries to OneStream, and immediately retrieve the results. Our CPM data is very valuable to client processes, and we've been able to accomplish these types of queries in the previous implementation of CPM at my company.
We are currently using OneStream XF 6.3.0
I'm assuming you are trying to pull data from OneStream to consume in external tools. I would say a combination of FDX and REST API might get you there.
You can use FDX to pull from a dataunit or stage. Since this works only on level zero, you might have to get creative with your rule to pull using functions.
Shameless plug, there is a chapter in our book that talks about FDX and external SQL database in our book.