Transactional Data in TM1

[dssd]

User has asked for Transactional data to be included in TM1 is it a good idea?

[dusherwo]

No.
In TM1, dimension elements must be unique. (Some OLAP engines work a little differently, allowing duplicates in different parts of the hierarchy, but TM1 doesn't.) Unless you invent a transaction ID, or use a user-hostile ID you have in the source system, you don't have a good way of loading the transactions in.
A better approach is to hold the transactions in a data mart and drillthrough to them.

[OLAPBPMguy]

Define "included in TM1".  I agree with Dusherwo that an OLAP cube is not a good transactional store.  If drill-through is well implemented then the transactions are at users' fingertips and the user never leaves the UI in which they are using TM1 so in fact to the user the solution is integrated, even to the point where they might not realise that the data in the drill is coming from somewhere else.  If explained properly a requirement like holding transactions in TM1 will likely disappear.

It also depends on what kind of transaction volumes you are talking about.  If the volumes aren't large than it may still be workable. If there is no source system and there is a requirement to capture end user data entry changes in TM1 as "transactions" (this often happens in public sector budgeting models for example) then there may be no alternative. But really OLAP is not that well suited to holding transactions.