Subject Transactions
Please help my understand what will happen in the following cases involving transactions.
System: Delphi XE2, Firebird 2,5x, Using DBX components.  Isolation level: ReadCommitted.

The actual statements are much more complex and involves various statements in the transaction and/or triggers that updates/insert into up to 8 tables.

Case 1
App 1 starts a transaction (T1) and in an After Insert trigger for MasterTable do something like:
Update TableSub set X = X + MasterTable.X where Y=Y.MasterTable
Before App1 commits, App2 starts a transtaction (T2) and  does the same statement.  Then App1 commits(T1) and then App2 commits(T2).  
Will this result in a deadlock or will T1 "run" and then T2 or will X.old in both transaction have the same value?

Case 2
Same case as above but the trigger use X = GEN_ID(Generator1,1).  
Will X be, for example 10, in T1 and 11 in T2, or will it result in a deadlock, or will X be 10 in both transactions?

Any information will be appreciated and even more so hints as on how to handle this.  I would like T1 to start and run to completion and then T2 taking into account what happen in T1.

Kind Regards

Cornie van Schoor
InfoStar Software
South Africa