Issue

When running processes concurrently, for example, by using this code:

                ExecutorService exec = Executors.newCachedThreadPool();
                exec.submit(new Runnable(){
                        @Override
                        public void run() {
                                // start a new process instance
                                ProcessInstance proc = ksession.startProcess("com.example.bpms.simplesupplyitemapproval", params);
        });
                exec.submit(new Runnable(){
                        @Override
                        public void run() {
                                // start a new process instance
                                ProcessInstance proc = ksession.startProcess("com.example.bpms.simplesupplyitemapproval", params); 
                        }
        });

It ends with following exception:

ERROR: Unique index or primary key violation: "PRIMARY_KEY_C6 ON PUBLIC.ORGANIZATIONALENTITY(ID)"; SQL statement:
insert into OrganizationalEntity (DTYPE, id) values ('User', ?) [23505-168]

However, if the threads are removed and simply invoke the process twice using new Runtime engines, it will work.

What would cause this Primary Key Exception?