Scheduler and Load Balancing

[Former Member]

Hi all,

I understood that a way to make an xMII 12 application fully scalable is using the cluster features of Netweaver. In this way we can have multiple dialog instances which are load balanced by a dispatcher so every application server receives a fraction of the global requests to MII.

If this is correct, I have a question about the scheduler.

Is a scheduled transaction executed only in one of the clustered application server or not? I mean, at a given time can I have the same scheduled transaction that runs on multiple servers or does Netweaver assure that the scheduled transactions runs only on one server?

This is an important design issue to consider, to properly avoid potential concurrency problem.

In our solution (not clustered yet) a scheduled transaction reads data from a table in a database. We are assuming that at a given time only one thread can access this table. Is this assumption still correct in a clustered environment?

Thank you

[Former Member]

Hi Mauro,

your question is related to my question about "how to strictly serialize MII TXs" some postings below. This has not yet been answered. As I

understand the architecture the scheduler uses a queue to fire the scheduled jobs. If this is the case then there is a MII MDB listening for the

job messages. With one instance running one can serialize the messages with limiting the MDB instances to 1. There is no way in a cluster.

Synchronizing a cluster can only be done on database via serializeable database transactions. That is how we normally do it in J2EE environments. So I would adhere to your question and ask:

1. Is the job scheduling done via JMS queues?

2. If so where can the number of instances of listeners to this queue be limited to 1?

3. Is it possible to synchronize transactions that are scheduled and that can be manually triggered?

3. Is there a way to serialize in a cluster without going through custom actions?

Related to this questions I would like to know if there is a MII standard way to communicate with MDBs and SLSBs written in NW? To say is it possible to send JMS messages or to call directly stateless sessio beans?

Regards,

Matthias