What are the messages marked as DEBUG in jazz.log?

Recently our RTC server ran out memeory and we got messages like:

CRJAZ0852I An exception occurred while executing the task "notification.mail", contributed by component "com.ibm.team.workitem". The task will be removed from the schedule.
java.lang.OutOfMemoryError

One hour after restarting the server, we satrted to see messages marked as DEBUG in the log:

2010-03-19 17:02:15,488 DEBUG repository.service.internal.rdb.RepositoryDatabase - CRJAZ0538I >>TX>> Beginning com.ibm.team.repository.service.internal.rdb.RepositoryDatabase$ReadTransaction on: 681126041
2010-03-19 17:02:15,489 DEBUG repository.service.internal.rdb.RepositoryDatabase - CRJAZ0543I >>TX>> Completing com.ibm.team.repository.service.internal.rdb.RepositoryDatabase$ReadTransaction on: 681126041
2010-03-19 17:02:15,489 DEBUG repository.service.internal.rdb.RepositoryDatabase - >>>>>>>>>>>>>>>>>>REPO ROLLBACK<<<<<<<<<<<<<<<<<<<<<<2010>>TX>> Beginning com.ibm.team.repository.service.internal.rdb.RepositoryDatabase$ReadTransaction on: 681126041
2010-03-19 17:02:16,720 DEBUG ository.service.internal.RdbRepositoryDataMediator - -- start queryData
.....

2010-03-19 17:04:40,733 DEBUG repository.service.internal.rdb.RepositoryDatabase - >>>>>>>>>>>>>>>>>>REPO ROLLBACK<<<<<<<<<<<<<<<<<<<<<<2010>>TX>> Beginning com.ibm.team.repository.service.internal.rdb.RepositoryDatabase$ReadTransaction on: 644818543
2010-03-19 17:04:40,733 DEBUG repository.service.internal.rdb.RepositoryDatabase - CRJAZ0543I >>TX>> Completing com.ibm.team.repository.service.internal.rdb.RepositoryDatabase$ReadTransaction on: 644818543
2010-03-19 17:04:40,733 DEBUG repository.service.internal.rdb.RepositoryDatabase - >>>>>>>>>>>>>>>>>>REPO ROLLBACK<<<<<<<<<<<<<<<<<<<<<<2010>>TX>> Beginning com.ibm.team.repository.service.internal.rdb.RepositoryDatabase$ReadTransaction on: 644818543
2010-03-19 17:04:40,734 DEBUG repository.service.internal.rdb.RepositoryDatabase - CRJAZ0543I >>TX>> Completing com.ibm.team.repository.service.internal.rdb.RepositoryDatabase$ReadTransaction on: 644818543
2010-03-19 17:04:40,734 DEBUG repository.service.internal.rdb.RepositoryDatabase - >>>>>>>>>>>>>>>>>>REPO ROLLBACK<<<<<<<<<<<<<<<<<<<<<<
2010-03-19 17:04:40,734 DEBUG sqlTxLogger - com.ibm.db2.jcc.t4.b@1b311b31 NO DB ROLLBACK

Then, the messages stopped.

Next day we had to restarted the server again due to other issues, including:

2010-03-20 11:13:04,581 ERROR com.ibm.team.repository - Could not connect to SMTP host: localhost, port: 25;
nested exception is:
java.net.SocketException: Too many open files

So why are those messages marked as DEBUG? It is because someone started the server in DEBUG mode but why it disappered in a few minutes?