Does TPX have any issues with the setting ALLOWUSERKEYCSA(NO) in member DIAGxx of SYS1.PARMLIB?
With ALLOWUSERKEYCSA(NO) it will depend upon how you have SRBEXIT defined in your VTAM members.
If TPX is configured to run with SRBEXIT=YES in VTAM Major Node Member, ALLOWUSERKEYCSA(NO) will keep TPX from allocating CSA in user keys and should not be a problem.
If instead SRBEXIT=NO is specified in the VTAM Major Node Member, ALLOWUSERKEYCSA(NO) prevents user key CSA from being allocated by failing any attempt to obtain user key from a CSA subpool (through GETMAIN or STORAGE|OBTAIN) with a B04-5C, B0A-5C, or B78-5C abend.
Release: NVINAM00200-5.4-TPX-Session Management-Access Management package