>VFP will block multiple calls to the same method, until previous calls have completed. So, if you have a routine that takes 1 second to run, and you call it every 1.5 seconds, you'll be ok. But, if you have a routine that takes 5 minutes to run, the first call will execute, but subesquent calls will wait in queue. Fixing this is a high priority for the Fox team.
That's not entirely right...
VFP will block multiple calls to the same *server*. Only totally separate
components (ie. another instance of the runtime) get concurrency.
Kim, MTS in its current form is not much more than an MS marketing ploy
IMHO. It doesn't do much for typical applications even if the client
tool does properly support Apartment Model Threading. It does nothing
for scalability, but it does provide some nice infrastructure features
(role based security and package deployment and installation). Also,
if you're working with multiple SQL backends heterogenous transactions
are useful.
The main useful feature though is the ability to define transactions
on the application level rather than at the database level. You can
group object method calls into transactions and then undo all of the
object calls from one spot in the application. OTOH, this works
realistically only against a data backend that supports distributed
transactions, which currently is only SQL server (the new Oracle
ODBC/OleDB drivers may support it as well). This is a great feature
*if* you really need it, but I venture to guess that few applications
have a need to do this in real life. Some of these issues are
much better addressed with proper component design.
These features come at a price though - there's a fair amount of
overhead calling an intermediary (MTX packages) that handle the
underlying calls to the actual COM objects. Since MTS currently
does not provide any server pooling features this is a problem
since objects need to be reloaded more often than they would be
if you cnonected directly to the servers.
This may or may not be addressed in the near future. From what I've
seen of MS's plans for COM and MTS pooling appears to not be high
on the list - in my personal experience though pooling is the make
or break feature that scalable applications must support.
+++ Rick ---
