Database transactions in i5/OS™ are scoped to the job or the activation group.
If your multithreaded application is working on multiple database transactions in multiple threads simultaneously, it is possible that a commit operation in one thread also commits activity done by another thread.
For example, an application has a thread that is working on a database transaction for client1 and another thread working on a database transaction for client2. The thread that is processing for client1 completes its processing and commits the changes. This commit operation also commits all the changes made for client2. Your application must be aware of the in-flight transactions that are in progress.