Why do I see "Could not commit with auto-commit set on" in the log?

A customer encountered the following problem. I am posting it here in case others encounter it. I will post a separate answer with detail on the cause of the problem.

ItemCleanupTask becomes unscheduled. This can result in a large backlog of items in the database that are no longer "live" in CLM.

In the ccm.log file, there is this exception.

015-04-14 10:07:23,289 [ccm: AsynchronousTaskRunner-12 @@ 10:07] ERROR com.ibm.team.repository                             - CRJAZ0852I An exception occurred while executing the task "ItemCleanupTask", contributed by component "com.ibm.team.repository".  The task will be removed from the schedule.
com.ibm.team.repository.common.TeamRepositoryException: Could not commit with auto-commit set on
at com.ibm.team.repository.service.internal.rdb.RepositoryDatabase$Transaction.finishTransaction(RepositoryDatabase.java:622)
at com.ibm.team.repository.service.internal.rdb.RepositoryDatabase$2.run(RepositoryDatabase.java:352)
at com.ibm.team.repository.service.internal.rdb.ConnectionPoolService.withCurrentConnection(ConnectionPoolService.java:470)
at sun.reflect.GeneratedMethodAccessor194.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
at java.lang.reflect.Method.invoke(Method.java:611)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord.invoke(ExportProxyServiceRecord.java:361)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord.access$0(ExportProxyServiceRecord.java:347)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord$ExportedServiceInvocationHandler.invoke(ExportProxyServiceRecord.java:56)
at com.sun.proxy.$Proxy7817.withCurrentConnection(Unknown Source)
at com.ibm.team.repository.service.internal.rdb.RepositoryDatabase.runTransaction(RepositoryDatabase.java:348)
at com.ibm.team.repository.service.internal.rdb.RepositoryDatabase.runInTransaction(RepositoryDatabase.java:288)
at com.ibm.team.repository.service.internal.PrimitiveTransactionService.runInTransaction(PrimitiveTransactionService.java:96)
at sun.reflect.GeneratedMethodAccessor61.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
at java.lang.reflect.Method.invoke(Method.java:611)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord.invoke(ExportProxyServiceRecord.java:361)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord.access$0(ExportProxyServiceRecord.java:347)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord$ExportedServiceInvocationHandler.invoke(ExportProxyServiceRecord.java:56)
at com.sun.proxy.$Proxy7850.runInTransaction(Unknown Source)
at com.ibm.team.repository.service.internal.dataaccess.delete.ItemCleanupService.completePartialItemDeletions(ItemCleanupService.java:141)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
at java.lang.reflect.Method.invoke(Method.java:611)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord.invoke(ExportProxyServiceRecord.java:361)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord.access$0(ExportProxyServiceRecord.java:347)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord$ExportedServiceInvocationHandler.invoke(ExportProxyServiceRecord.java:56)
at com.sun.proxy.$Proxy7869.completePartialItemDeletions(Unknown Source)
at com.ibm.team.repository.service.internal.ItemCleanupTask.runTask(ItemCleanupTask.java:22)
at com.ibm.team.repository.service.async.AbstractAutoScheduledTask.executeTask(AbstractAutoScheduledTask.java:96)
at sun.reflect.GeneratedMethodAccessor136.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
at java.lang.reflect.Method.invoke(Method.java:611)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord.invoke(ExportProxyServiceRecord.java:361)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord.access$0(ExportProxyServiceRecord.java:347)
at org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord$ExportedServiceInvocationHandler.invoke(ExportProxyServiceRecord.java:56)
at com.sun.proxy.$Proxy7916.executeTask(Unknown Source)
at com.ibm.team.repository.service.internal.scheduler.AsynchronousTaskRunner.runTask(AsynchronousTaskRunner.java:185)
at com.ibm.team.repository.service.internal.scheduler.AsynchronousTaskRunner.run(AsynchronousTaskRunner.java:138)
at java.lang.Thread.run(Thread.java:790)
Caused by: java.sql.SQLException: Could not commit with auto-commit set on
at oracle.jdbc.driver.PhysicalConnection.commit(PhysicalConnection.java:2356)
at oracle.jdbc.driver.PhysicalConnection.commit(PhysicalConnection.java:2403)
at com.ibm.team.repository.service.internal.db.jdbcwrappers.stat.ConnectionStatWrapper.commit(ConnectionStatWrapper.java:155)
at com.ibm.team.repository.service.internal.db.jdbcwrappers.errlog.ConnectionErrLogWrapper.commit(ConnectionErrLogWrapper.java:88)
at com.ibm.team.repository.service.internal.db.jdbcwrappers.leak.ConnectionLeakWrapper.commit(ConnectionLeakWrapper.java:134)
at com.ibm.team.repository.service.internal.rdb.RepositoryDatabase$WriteExclusiveTransaction.completeTransaction(RepositoryDatabase.java:787)
at com.ibm.team.repository.service.internal.rdb.RepositoryDatabase$Transaction.finishTransaction(RepositoryDatabase.java:603)
... 40 more