Threadsafe SYNCPOINT and Other Commands
CICS commands that were made threadsafe in CICS TS 4.2 include named counter server commands, QUERY SECURITY, SIGNON, SIGNOFF, VERIFY PASSWORD, CHANGE PASSWORD, EXTRACT TCPIP and EXTRACT CERTIFICATE, along with several new SPI commands. Most significant, however, is the SYNCPOINT command.
The CICS Recovery Manager domain now processes a SYNCPOINT command on an open TCB where possible to minimize TCB switching. Syncpoint processing can occur on an open TCB for all resource types declared as threadsafe that were accessed in the unit of work. If resource types not declared as threadsafe were accessed in the unit of work, the Recovery Manager switches to the QR TCB for those resource types. Prior to CICS TS 4.2, CICS would switch to the QR TCB prior to the end of task sync point. In CICS TS 4.2, the application remains on an open TCB, if it’s running on one, until end of task sync point is called. Afterward, CICS switches to QR for the task detach logic.
Prior to CICS TS 4.2, a threadsafe application running on an open TCB that had, for example, updated DB2 and WebSphere MQ and then issued a sync point, would require nine TCB switches:
- A switch to QR would be made at the start of the sync point.
- Switches to L8 and back to QR would occur when calling DB2 for PREPARE.
- Switches to L8 and back to QR would occur when calling WebSphere MQ for PREPARE.
- Switches to L8 and back to QR would occur when calling DB2 for COMMIT.
- Switches to L8 and back to QR would occur when calling WebSphere MQ for COMMIT.
In CICS TS 4.2, if a transaction is terminal-driven, one TCB switch to QR will occur. For a non-terminal-driven transaction (and assuming no other non-threadsafe resources were touched), no TCB switches occur.
CICS TS 4.2 contains major changes to provide a CICS domain architecture environment that exploits the underlying z/Architecture for 64-bit addressing, and to provide the infrastructure for the future. This has allowed exploitation by CICS services in CICS TS 4.2, and lays the foundation for future CICS applications to be able to use and exploit 64-bit addressing mode. The exploitation of the 64-bit addressing provided by the z/Architecture enables CICS to remove some of the previous limitations that affect scalability and availability by delivering large address spaces.
CICS can use z/OS 64-bit virtual storage to increase capacity by supporting more concurrent users and concurrent transactions. CICS can also keep up with the virtual storage demands of increased workloads for existing applications and the larger memory requirements of new applications and new technologies.
CICS domains can use stack storage and domain anchor storage, and can allocate domain control blocks in virtual storage above the bar. Kernel, Monitoring, Storage Manager, Lock Manager, Trace, Message and Temporary Storage are all CICS domains that now run AMODE 64 and keep their data above the bar.