The very first reason getting this abend in CICS is Load module of program or Map is not loaded at the time of CICS transaction execution.
I have compiled a new program, but i have not defined that program with PPT entry. So we can expect APCT abend. Similarly, I have written new map, so we need PPT ENTRY for new map.
Similarly, We need valid transaction entry in PPT. Else we will get APCT abend.
Please read my post on PPT entry.
When we are working first time in new CICS region, we may get many problems like this. So PPT entries of all CICS objects required.
DB2-database, we also need to do DB2entry for DB2 Sub-system.
The above are the reasons to get APCT abend. You can contact us if you have specific problem.