>>1: START TRANSACTION
>>2: WITHDRAW $50 from account 32146.
>>3: DEPOSIT $50 into account 12345.
>>4: LOG transfer (date/time/teller/etc...) for auditing.
>>5: COMMIT TRANSACTION
DK> It depends why step 3 failed.
DK> If you want to rollback the transaction to the beginning on any error,
DK> you simply use an 'on error' statement in VB to trap the error, and send
DK> a rollback command when the error is detected.
And what if the server lost connection with client computer ?
there must be automatic rollback after certain 'time-out' period
Data integrity logic should be ensured by client application (when to
call 'start transaction' and when to call 'commit'), the server task is to
ensure that logic - i.e. that at any given moment users see the
database in integrity state and not at some point within transaction processing.
If user has not commited transaction the database integrity state is
still at the point before start transaction was called.
Not user but server is responsible for rolling back not commited
transactions, user can only help relief the server from major part of this problem by
rollback as many failed transactions as he can. however user cannot be
responsible for rolling back all the transactions