How many number of database connections used in a transaction

Question

Hi All,
We are using weblogic 8.1 with Oracle 9i both running on windows 2000. We are trying to estimate the potential resource usage in the system we are building. As part of this activity we want to find out how the database connections are used for entity beans -
If a session bean calls more than one entity beans
(each method in the entity bean doing one update) does weblogic use the same database connection for all the entity beans or does it use seperate connections ? Is such behaviour documented somewhere ?
Here the assumption is all the entity beans are linked to the same datasource.
If the (default) behaviour is to use seperate connections is there a way to make it use one connection across multiple entity beans.
Thanks
Kingshuk

Answer 1

Hi Bodapati,
Sorry for the delay in replying to this.
There is optimization, which will use the XA
connections from the pool. Can you tell me what your
observations are? I may be able to see if we can tune it.From our tests the XA driver too appear to make use of one connection only for the life of the transaction. There is a good document here explaining how it is ensured that only one connection is used - http://e-docs.bea.com/wls/docs81/oracle/trxjdbcx.html#1083132
Quoting from the above URL :
When a thread attempts to use a connection, the XA jDriver calls xa_open (and xa_start) to create the connection and associate it with the thread. After the database connection is created, the connection remains associated with the thread; the driver does not call xa_close. When the thread subsequently needs a database connection, it uses the same database connection associated with it, even though it appears to get and return a connection from the JDBC connection pool
I am not sure why you say the connections will be
blocked. One connection will be blocked only if you are > using non-XA driver to setup the pool, until the
transaction commits. For XA there is no need to reserve
the same connection for the transaction.Probably my understanding on this is incorrect and I need to read up. I was under the impression that - once a transaction begins, each connection used within that transaction, is enlisted as a part of that transaction and can not be used by in another transaction until the transaction commits or rollsback.
Thanks
Kingshuk