diff --git a/hibernate-core/src/main/java/org/hibernate/dialect/Database.java b/hibernate-core/src/main/java/org/hibernate/dialect/Database.java
index 0e323ae5647e..18720bd65145 100644
--- a/hibernate-core/src/main/java/org/hibernate/dialect/Database.java
+++ b/hibernate-core/src/main/java/org/hibernate/dialect/Database.java
@@ -44,11 +44,15 @@ public Dialect createDialect(DialectResolutionInfo info) {
 						return new DB2zDialect( info );
 					}
 					case "QSQ": {
-						// i
+						// i, this only works if "use drda metadata version" property is set to true in the drivers properties
 						return new DB2iDialect( info );
 					}
 				}
 			}
+			if ("DB2 UDB for AS/400".equals(info.getDatabaseName())) {
+				// i
+				return new DB2iDialect( info );
+			}
 
 			return new DB2Dialect( info );
 		}
diff --git a/hibernate-core/src/main/java/org/hibernate/engine/jdbc/connections/internal/DriverManagerConnectionProviderImpl.java b/hibernate-core/src/main/java/org/hibernate/engine/jdbc/connections/internal/DriverManagerConnectionProviderImpl.java
index 6bc006024660..e6cdc2a49ea9 100644
--- a/hibernate-core/src/main/java/org/hibernate/engine/jdbc/connections/internal/DriverManagerConnectionProviderImpl.java
+++ b/hibernate-core/src/main/java/org/hibernate/engine/jdbc/connections/internal/DriverManagerConnectionProviderImpl.java
@@ -472,7 +472,9 @@ protected void closeConnection(Connection conn, Throwable t) {
 				}
 			}
 			finally {
-				allConnections.remove( conn );
+				if ( !allConnections.remove( conn ) ) {
+					ConnectionInfoLogger.INSTANCE.debug( "Connection remove failed." );
+				}
 			}
 		}
 
diff --git a/hibernate-core/src/main/java/org/hibernate/engine/jdbc/env/internal/JdbcEnvironmentInitiator.java b/hibernate-core/src/main/java/org/hibernate/engine/jdbc/env/internal/JdbcEnvironmentInitiator.java
index bcd86a040922..8588501c8786 100644
--- a/hibernate-core/src/main/java/org/hibernate/engine/jdbc/env/internal/JdbcEnvironmentInitiator.java
+++ b/hibernate-core/src/main/java/org/hibernate/engine/jdbc/env/internal/JdbcEnvironmentInitiator.java
@@ -326,13 +326,11 @@ protected JdbcEnvironmentImpl getJdbcEnvironmentUsingJdbcMetadata(
 				new SqlExceptionHelper( false ),
 				registry
 		);
-		temporaryJdbcSessionOwner.transactionCoordinator = registry.requireService( TransactionCoordinatorBuilder.class )
-				.buildTransactionCoordinator(
-						new JdbcCoordinatorImpl( null, temporaryJdbcSessionOwner, jdbcServices ),
-						() -> false
-				);
+		final JdbcCoordinatorImpl jdbcCoordinator = new JdbcCoordinatorImpl( null, temporaryJdbcSessionOwner, jdbcServices );
 
 		try {
+			temporaryJdbcSessionOwner.transactionCoordinator = registry.requireService( TransactionCoordinatorBuilder.class )
+					.buildTransactionCoordinator( jdbcCoordinator, () -> false );
 			return temporaryJdbcSessionOwner.transactionCoordinator.createIsolationDelegate().delegateWork(
 					new AbstractReturningWork<>() {
 						@Override
@@ -404,6 +402,10 @@ private int databaseMicroVersion(DatabaseMetaData metadata) throws SQLException
 		catch ( Exception e ) {
 			log.unableToObtainConnectionToQueryMetadata( e );
 		}
+		finally {
+			//noinspection resource
+			jdbcCoordinator.close();
+		}
 		// accessing the JDBC metadata failed
 		return getJdbcEnvironmentWithDefaults( configurationValues, registry, dialectFactory );
 	}
diff --git a/hibernate-core/src/test/java/org/hibernate/orm/test/dialect/resolver/DialectFactoryTest.java b/hibernate-core/src/test/java/org/hibernate/orm/test/dialect/resolver/DialectFactoryTest.java
index 65b1c8d24de7..2f648db51892 100644
--- a/hibernate-core/src/test/java/org/hibernate/orm/test/dialect/resolver/DialectFactoryTest.java
+++ b/hibernate-core/src/test/java/org/hibernate/orm/test/dialect/resolver/DialectFactoryTest.java
@@ -156,8 +156,8 @@ public void testPreregisteredDialects() {
 		testDetermination( "DB2/SUN", DB2Dialect.class, resolver );
 		testDetermination( "DB2/LINUX390", DB2Dialect.class, resolver );
 		testDetermination( "DB2/AIX64", DB2Dialect.class, resolver );
-		testDetermination( "DB2 UDB for AS/400", DB2Dialect.class, resolver );
-		testDetermination( "DB2 UDB for AS/400", 7, 3, DB2Dialect.class, resolver );
+		testDetermination( "DB2 UDB for AS/400", DB2iDialect.class, resolver );
+		testDetermination( "DB2 UDB for AS/400", 7, 3, DB2iDialect.class, resolver );
 		testDetermination( "Oracle", 8, OracleDialect.class, resolver );
 		testDetermination( "Oracle", 9, OracleDialect.class, resolver );
 		testDetermination( "Oracle", 10, OracleDialect.class, resolver );
diff --git a/hibernate-testing/src/main/java/org/hibernate/testing/jta/JtaAwareConnectionProviderImpl.java b/hibernate-testing/src/main/java/org/hibernate/testing/jta/JtaAwareConnectionProviderImpl.java
index f90e6ad9ae9d..1964e46281d5 100644
--- a/hibernate-testing/src/main/java/org/hibernate/testing/jta/JtaAwareConnectionProviderImpl.java
+++ b/hibernate-testing/src/main/java/org/hibernate/testing/jta/JtaAwareConnectionProviderImpl.java
@@ -214,7 +214,7 @@ private void delist(Connection connection) {
 			System.err.println( "!!!Error trying to reset synchronization registry!!!" );
 		}
 		try {
-			delegate.closeConnection( connection );
+			delegate.closeConnection( ((ConnectionWrapper) connection).delegate );
 		}
 		catch (SQLException e) {
 			System.err.println( "!!!Error trying to close JDBC connection from delist callbacks!!!" );