LOCK TABLE pg_class IN EXCLUSIVE MODE

 try (Statement stmt = jdbcConn.createStatement()) {
                    jdbcConn.setAutoCommit(true);

                    long thisSessionId;
                    try (ResultSet current = stmt.executeQuery("SELECT VALUE FROM INFORMATION_SCHEMA.SYSTEM_SESSIONINFO WHERE key ='SESSION ID'")) {
                        current.next();
                         thisSessionId = current.getLong(1);
                    } catch (Exception e){
                        throw new RuntimeException(e);
                    }

                    stmt.executeUpdate("CREATE TABLE IF NOT EXISTS CHANGELOG_LOCK (SESSION_ID BIGINT PRIMARY KEY)");
                    stmt.executeUpdate("INSERT INTO CHANGELOG_LOCK (SESSION_ID) VALUES (" + thisSessionId + ")");

                    for (; ; ) {
                        stmt.executeUpdate("DELETE FROM CHANGELOG_LOCK WHERE NOT SESSION_ID IN (SELECT SESSION_ID FROM INFORMATION_SCHEMA.SYSTEM_SESSIONS)");
                        try (ResultSet rst = stmt.executeQuery("SELECT 1 FROM CHANGELOG_LOCK HAVING MIN(SESSION_ID)=" + thisSessionId)) {
                            if (!rst.next()) {
                                Thread.sleep(100);
                                continue;
                            }

                            ..... синхронный код ... 
                            ..... синхронный код ... 
                            ..... синхронный код ... 


                            break;
                        }
                    }
                    return null;
                } catch (Exception e) {
                    e.printStackTrace();
                    throw new RuntimeException();
                }

                    stmt.executeUpdate("CREATE TABLE IF NOT EXISTS CHANGELOG_LOCK (SESSION_ID BIGINT, SEQ BIGINT PRIMARY KEY)");
                    stmt.executeUpdate("CREATE SEQUENCE IF NOT EXISTS CHANGELOG_SEQ");
                    stmt.executeUpdate("INSERT INTO CHANGELOG_LOCK (SESSION_ID, SEQ) VALUES (" + thisSessionId + ", nextval('CHANGELOG_SEQ'))");

                    for (; ; ) {
                        stmt.executeUpdate("DELETE FROM CHANGELOG_LOCK WHERE NOT SESSION_ID IN (SELECT SESSION_ID FROM INFORMATION_SCHEMA.SYSTEM_SESSIONS)");
                        try (ResultSet rst = stmt.executeQuery("SELECT 1 FROM CHANGELOG_LOCK WHERE SESSION_ID=" + thisSessionId + " ORDER BY SEQ")) {

"SELECT SESSION_ID FROM CHANGELOG_LOCK ORDER BY SEQ"