Due to the lack of support for hibernate.jdbc.batch_size in DB2 and Sybase:

http://www.hibernate.org/120.html#A6

We have removed the benefit of JDBC batching processing on all of our databases. For example, some upgrade tasks that do batch inserts/updates/deletes could run faster with batching enabled.

This does not have to be the case. We can apply the batch setting on a per dialect basis by updating:

com.atlassian.config.db.HibernateConfig#getHibernateProperties

We can determine the dialect by querying applicationConfig.