On r16 and earlier releases, these temporary work datasets, were built using a high level qualifier of variable ZUSER (ISPF USERID). Some sites, however, did not allow datasets to be prefixed by a users userid. The code was therefore changed to use the TSO PROFILE PREFIX instead. Unfortunately for users at some sites, with TSO PROFILE NOPREFIX specified, this code change has meant that TSO PROFILE PREFIX has to be specified, to allow the use of PREFIX in allocating these datasets.
Subsequently PTF UO00625 on r18 has been released. Now when a user has NOPREFIX specified, then we will automatically switch to using ISPF USERID.