Subject Deadlock because of limbo transaction
Author Guido Klapperich
I have two databases, one server database and one client database on a
laptop. Every day data is imported from the server to the client
database. My app works like this:

1) Connect to the server and client database within one transaction
(using the 2PC protocol)
2) Look in table SYNC_TASKS if there is synchronization task for me
3) If a task is found, log the start of the synchronization task
4) Synchronize the data
5) Log the end of the synchronization task
6) commit transaction
7) disconnect from both databases

Now at point 5) the network connection has been interrupted and
therefore the transaction is left in limbo state. So far all is clear to me.
Now when I start my app, I get at point 2) the following error
Error: ISC ERROR CODE:335544459
record from transaction 59681 is stuck in limbo

I don't understand, why a select on table SYNC_TASKS causes a deadlock.
I thought, because of the multi generation architecture of FB it is
impossible to create a deadlock, when reading data.
Perhaps someone can tell me where my error in reasoning is.