We have made a POS system.
Made in Delphi 2010.
Its made of 2 seperate programs. A backend and a frontend. backend uses TIB to communicate with the database.
Frontend uses IBObjects.

The program will do a lot of read-committed.
Upon an update/insert/delete the program will do a start transaction ... do whatever insert/update/delete ... Commit.All in a try...except with a rollback in the except. No user inpt from start to commit.

I am pretty sure we do not use any prepare anyware.
I will check though.

I am aware that you cant give a more precise answer sinse you dont know the programs.
This limbo transaction has only happen 3 times over the past 1½ year. And only on one database.

The programs we make are the same to every user. Database as well.