comitting transaction from JMS queue to target RDBMS ?

Hi ,
How is the transaction comit algoritm of ART when writing data from JMS queue to target database ( Oracle ) ?
Does it comit record by record or writing after all records ?
It seems that the slowest part of an initial state is when writing from jms queue to the target database.
Is there any parameter that I can effect it ?
Kind regards
Engin