Dear Friends

i've heard that long running transaction(updatable) affect performance.

what can be said long running transaction
i mean how long is long and with how many users and how it affects ,
will my select queries get slow down ?(how much) ?

can transaction - open for 16 hour with 15 users be said long running and
does it affect performance ?

does it affects performance of transactions aginst that perticular tables
(on which
transaction is running) or
does it affect performance for whole database for all the tables


Thanks
Kamlesh