The CONFIG member parameter PSOUNIT is designed and described in XCOM official documents:
However, we discovered and identified PSOUNIT is NOT working as it is supposed to.
Although explained as "The only 2 parameters considered when the temp dataset is allocated are the PSOPREF and the PSOVOL. The PSOUNIT is not considered in this case. Another parameter it will use is the VOL= if you don't have a value for PSOVOL= and have something for VOL=." Hard-coding PSOVOL= and VOL= is really a bad approach and refused by our storage group, it will cause lots of mess up over the time.
Here is another workaround from CA "In reference to the PSOUNIT and your conversation with Bruce, you must use UNIT=." But after testing, UNIT= is used by both normal dataset and temp dataset, it will cause data integrity issue as well and cannot be accepted since the normal dataset can be put on the temp volume and is subjected to cleanup.
It is also explained as "With regard to the PSOUNIT parameter, as of this moment, the documentation is wrong. While I can see an advantage to having a PSOUNIT parameter for this purpose, it is not designed to work that way today. Please open an IDEA on the communities page for XCOM and it will be taken into consideration along with our other development projects which are constantly being reviewed for inclusion in the product."
Since the IDEA is here already and originally designed/documented and supposed to be implemented. So it should be a bug or at least a defect.
The solution should be really easy and simple by adding a if-statement logic and hopefully it can be fixed soon.