TCB statistics

The task control block (TCB) dispatcher statistics report the amount of CPU time consumed by each CICS® TCB since the last time statistics were reset.

To calculate the approximate time since CICS statistics were last reset, add the values of Accum time in MVS™ wait and Accum time dispatched. To calculate the percentage usage of each CICS TCB, divide the value of Accum CPU time/TCB by the time since CICS statistics were last reset (as calculated earlier).

The Accum CPU time/TCB value does not include uncaptured time. Therefore, when you use this calculation, even a very busy CICS TCB is noticeably less than 100% busy. If the calculation indicates that a CICS region is more than 70% busy, you are approaching the capacity of the region. However, the 70% calculation can be only approximate. The capacity of the region depends on such factors as the workload in operation, the mix of activity in the workload, and which release of CICS you are currently using. You can use Resource Measurement Facility (RMF) to obtain a definitive measurement to use in your calculation, or you can use RMF with your monitoring system. For more information, see the z/OS Resource Measurement Facility (RMF) Report Analysis.

Note: Accum time dispatched is not a measurement of CPU time. MVS can run higher priority work, for example all I/O activity and higher priority regions, without CICS being aware.

TCB modes are as follows:

QR: There is always one quasi-reentrant mode TCB. It is used to run quasi-reentrant CICS code and non-threadsafe application code.
FO: There is always one file-owning TCB. It is used for opening and closing user data sets.
RO: There is always one resource-owning TCB. The RO TCB is used for loading programs, unless the command to load the program (EXEC CICS LOAD, XCTL, or LINK) is issued by an application that is currently running on an open TCB. In that situation, the open TCB is used to load the program instead of the RO TCB. The RO TCB is also used for opening and closing CICS data sets, issuing RACF® calls, and similar tasks.
The CICS loader domain global statistics record the number of program load operations that took place on the RO TCB, and the time taken for them. You can compare these values to the overall statistics for the number and time of program load operations, to see the proportion of program load operations that took place on open TCBs instead of the RO TCB.
CO: The optional concurrent mode TCB is used for processes that can safely run in parallel with other CICS activity such as VSAM requests. Define the system initialization parameter SUBTSKS using the value 0 or 1 to specify whether there is a CO TCB.
D2: The D2 mode TCB is used to stop Db2® protected threads. Protected threads are stopped in the normal purge cycle, or when a user issues the DSNC DISCONNECT plan-name command, which stops the protected threads for a plan immediately.
SZ: The single optional SZ mode TCB is used by the FEPI interface.
RP: The single optional RP mode TCB is used to make ONC/RPC calls.
EP: The EP mode TCBs are used to run event processing in a CICS region. The TCBs either dispatch events to an appropriate EP adapter or defer filtering of system events.
L8: A task has an L8 mode TCB for its sole use when it calls a program that is enabled with the OPENAPI option and is defined with EXECKEY=CICS, or when it calls a task-related user exit program that is enabled with the OPENAPI option. An L8 TCB is used when CICS uses the CICS-MQ adapter to connect to WebSphere® MQ Version 6 or later and when CICS connects to DB2® Version 8 or earlier.
L9: A task has an L9 mode TCB for its sole use when it calls a program that is enabled with the OPENAPI option and is defined with EXECKEY=USER.
SO: The SO mode TCB is used to make calls to the socket interface of TCP/IP.
SL: The SL mode TCB is used to wait for activity on a set of listening sockets.
S8: A task uses an S8 TCB if it needs to use the system Secure Sockets Layer (SSL). A task also uses an S8 TCB if it needs to use LDAP over the DFHDDAPX XPI interface. The TCB is used only for the duration of the SSL negotiation or the LDAP request. On completion, the TCB is released back into the SSL pool to be reused.
SP: The SP mode TCB is used for socket pthread owning tasks. It manages the SSL pool of S8 TCBs and owns the Language Environment® enclave that contains the SSL cache.
T8: A Java™ application running in a JVMSERVER uses a T8 TCB. The T8 will also be used for Db2 requests from Java applications when CICS is connected to DB2 Version 9 or later.
TP: The TP mode TCB owns and manages the Language Environment enclave, the JVM, the THRD TCB pool, and T8 TCBs of a JVM server.
X8: A task has an X8 mode TCB for its sole use when it calls a C or C++ program that is compiled with the XPLINK compiler option and defined with EXECKEY=CICS. The CICS-Db2 task-related user exit may use a X8 TCB if it is run with CONCURRENCY(REQUIRED) and API(CICSAPI).
X9: A task has an X9 mode TCB for its sole use when it calls a C or C++ program that is compiled with the XPLINK compiler option and defined with EXECKEY=USER.