You have upgraded from CICS Transaction Server for z/OS (CICS TS) V2.2 to CICS TS V2.3, or later, and receive message BPX1040I.
BPXI040I PROCESS LIMIT MAXPROCUSER HAS REACHED nnn% OF ITS CURRENT CAPACITY OF limtot FOR PID=pid IN JOB name RUNNING IN ADDRESS SPACE asid.
The way CICS TCBs were dubbed was changed in CICS TS V2.3 and above. Any daughter TCBs of the QR are now dubbed as a process. This increases the number of processes and might require an increase in the MAXPROCUSER value.
Diagnosing the problem
A dump of the CICS region shows that you are using "TCPIP Sockets for CICS" which can use up to 300-400 TCBs at any time. There are currently 300+ transactions started by the CSKL listener. These TCBs are not OPEN TCBs but rather use UNIX® System Services (USS). When running under CICS TS V2.2, these were not counted against MAXPROCUSER, but after CICS TS V2.2 they are counted.
Resolving the problem
Increase the value specified for MAXPROCUSER.
CICS/TS CICS TS CICS Transaction Server