QTEMP is a library created by OS/400 for each job.
QTEMP is very different from other libraries on the system.
Each job has its own QTEMP, separate from every other jobs QTEMP.
Conceptually QTEMP is like 'local variables' in a procedure, no other procedure can access a procedures 'local variables', similarly no other job can access a jobs QTEMP library or objects in the jobs QTEMP library.
The intent is that every job will have a place to store objects needed temporarily - for the duration of that particular job, and no longer.
The job's QTEMP library and all objects in it are deleted when the job ends.