It’s a library named QTEMP. But it’s special because every job always gets a QTEMP library assigned to that job. Every job has a different QTEMP. It’s just a temporary work library that goes away automatically when the job ends. Jobs cannot interfere with another job’s QTEMP. Anything you create in your job’s QTEMP library gets deleted when the job ends. — Tom

If you are going to use QTEMP for testing anything that is also in your current production environment make sure you LIBL is set properly. QTEMP must be located before the production libraries. I just usually move it to the first library in the list. The nice thing about using QTEMP is there is no housekeeping. When you log off all the object in QTEMP go away.