FireDAC is thread-safe if the following conditions are met:
- A connection object and all objects associated with it (such as TFDQuery, 
  TFDTransaction, and so on) are used by a single thread at each moment.

- FDManager is activated before threads start, by setting FDManager.Active to True.


This means that after a thread opens a query and until its processing is finished, 
the application cannot use this query and the connection objects in another thread. 
Similarly, after a thread starts a transaction and until the transaction is finished, 
the application cannot use this transaction and the connection objects in another thread.