Ashish Karalkar wrote:
> Yes, its true,but evn for 2/3 tables the replication
> doesnt start and same massage keeps flashing for a
> long time its more than 6 hours
>   
The diagnosis remains true.  Replication cannot start until the old
transactions (which are apparently being held open for over six hours)
complete.

This tells me that you've got a fairly serious problem with your
application and/or users, namely that they are holding transactions open
for a very long time.  If you cannot bring that condition under control,
you will find that Slony-I behaves rather badly.  Performance of
replication won't be very good, as some of the internals tables will
tend to bloat in size.

A universal principle in OLTP applications is that long running
transactions are a bad thing.  In some applications, the locks held will
tend to lead to lock escalation that leads to deadlocks (of the informal
sort).  With PostgreSQL, the trouble is that you'll see a lot of "crud"
build up in any tables that are heavily updated.

You should check to see why your applications/users are holding
transactions open for so long.  It should not normally be necessary to
hold a transaction open that long.