JPA + Postgres = autocommit?

Hello,

I am having a small but severe Problem with PostgreSQL. At our company, we are currently developing a business application in Java EE 7 running on a Payara (Glassfish fork) 4 server (with Eclipselink) and we are using Postgres 9.5 as our database and the postgresql-9.4.1208 JDBC driver. Now, it seems that the connection to the PostgreSQL database is in an autocommit mode. Transactions (both container and bean managed) cannot be rolled back, every single SQL command is executed and commited on flush().

Here is my persistence.xml:

<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd"
version="2.1">

<persistence-unit name="tsms_pdm" transaction-type="JTA">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<jta-data-source>jdbc/PDMDataSource</jta-data-source>

<properties>
<property name="eclipselink.jdbc.cache-statements" value="true" />
<property name="eclipselink.cache.shared.default" value="false" />
<property name="eclipselink.cache.type.default" value="NONE" />
<property name="javax.persistence.query.timeout" value="300000" />
</properties>
</persistence-unit>
</persistence>

And here is an excerpt from the Payara domain.xml:

<jdbc-connection-pool datasource-classname="org.postgresql.ds.PGSimpleDataSource" name="PDMDataSource" res-type="javax.sql.DataSource">
<property name="TargetServerType" value="any"/>
<property name="BinaryTransfer" value="true"/>
<property name="UnknownLength" value="2147483647"/>
<property name="DisableColumnSanitiser" value="false"/>
<property name="UseSpNego" value="false"/>
<property name="SspiServiceClass" value="POSTGRES"/>
<property name="ProtocolVersion" value="0"/>
<property name="LogLevel" value="0"/>
<property name="SendBufferSize" value="-1"/>
<property name="ReceiveBufferSize" value="-1"/>
<property name="LoadBalanceHosts" value="false"/>
<property name="ReadOnly" value="false"/>
<property name="LogUnclosedConnections" value="false"/>
<property name="DatabaseName" value="pdm"/>
<property name="GssLib" value="auto"/>
<property name="CurrentSchema" value="pdm"/>
<property name="PortNumber" value="5432"/>
<property name="DefaultRowFetchSize" value="0"/>
<property name="User" value="pdm_user"/>
<property name="Url" value="jdbc:postgresql://localhost/pdm?"/>
<property name="AllowEncodingChanges" value="false"/>
<property name="PrepareThreshold" value="5"/>
<property name="SocketTimeout" value="0"/>
<property name="HostRecheckSeconds" value="10"/>
<property name="Password" value="tssb"/>
<property name="ConnectTimeout" value="0"/>
<property name="PreparedStatementCacheQueries" value="256"/>
<property name="Compatible" value="9.4"/>
<property name="Ssl" value="false"/>
<property name="PreparedStatementCacheSizeMiB" value="5"/>
<property name="Loglevel" value="0"/>
<property name="LoginTimeout" value="0"/>
<property name="ServerName" value="localhost"/>
<property name="TcpKeepAlive" value="false"/>
</jdbc-connection-pool>
<jdbc-resource pool-name="PDMDataSource" jndi-name="jdbc/PDMDataSource"/>

Am I missing something here? How do I disable the autocommit? Any help would be greatly appreciated.

Best regards,
Yuriy
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