Problem with configuration of hibernate batch insert

Hibernate ORM
1

Hibernate batch insert is not working for me on Oracle database.

I have read

Having

hibernate.jdbc.batch_size=30
hibernate.order_inserts=true
hibernate.order_updates=true
hibernate.jdbc.batch_versioned_data=true

there are still 2 separate inserts into the same table one by one (logged via net.ttddyy.dsproxy.support.ProxyDataSourceBuilder, not only bare hibernate).

What can be a problem? How can I diagnose it?

Can type:prepared be a problem ? ( "type":"Prepared", "batch":false, )

2019-07-26 15:04:28.593 DEBUG 23724 --- [           main] org.hibernate.SQL                        : insert into STUDENT (version, ...) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
2019-07-26 15:04:28.594  INFO 23724 --- [           main] n.t.d.l.l.SLF4JQueryLoggingListener      : {"name":"Batch-Insert-Logger", "connection":4, "time":1, "success":true, "type":"Prepared", "batch":false, "querySize":1, "batchSize":0, "query":["insert into STUDENT (version, ...) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)"], "params":[["0",...]}
2019-07-26 15:04:28.594 DEBUG 23724 --- [           main] org.hibernate.SQL                        : insert into STUDENT (version, ...) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
2019-07-26 15:04:28.595  INFO 23724 --- [           main] n.t.d.l.l.SLF4JQueryLoggingListener      : {"name":"Batch-Insert-Logger", "connection":4, "time":1, "success":true, "type":"Prepared", "batch":false, "querySize":1, "batchSize":0, "query":["insert into STUDENT (version, ...) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)"], "params":[["0",...]]}

I have posted the same question to stackoverflow:
problem-with-configuration-of-hibernate-batch-insert