CA Datacom CICS Services Installation and Configuration Best Practices › Using CICS SYNCPOINT

Using CICS SYNCPOINT

Business Value

Simplified management of CA Datacom CICS Services resources using CICS SYNCPOINT implementation for user log type commands is available.

Important! Take great care to distinguish between user issued log commands and log commands that are issued as a result of SYNCPOINT. Both can generate the same log command, but they may not function the same way. A user issued log command is when an application issues a CA Datacom/DB request with its command being a log command.

Additional Considerations

Take advantage of the following simplifications:

• Synchronization of all resources is ensured.
• All LOGxx commands that checkpoint data participate in both the MVS LOGGER (or CICS JOURNAL FILE if z/VSE) and the LXX.
• SYNCPOINT optimization of DB logging commands is allowed.
• The original user log command is preserved on the CA Datacom/DB LXX file.

All updates for application issued SYNCPOINTs and task termination SYNCPOINTs are true for CA Datacom CICS Services r11 and Version 14.0. No difference between r11 and Version 14.0 exists for user-issued or CICS issued SYNCPOINTs.

When an application program issues a CICS SYNCPOINT, all held data resources but not the sets necessarily, are released. Released resources include all resources under exclusive control, and the release of threads making those resources available for batch jobs or other CICS tasks to hold and update. After an application issues a CICS SYNCPOINT, CA Datacom CICS Services participates in SYNCPOINT, and the task completes one unit of work (UOW). Coding a CICS SYNCPOINT commits all updates to all resources or backs them all out including the following:

• VSAM
• DL/I
• BDAM
• DB2
• CA Datacom/DB
• CICS SYNCPOINT ROLLBACK

Important! If you want SYNCPOINT ROLLBACK to back out the updates for a transaction, specify the parameter value DTB=YES in the appropriate TRANSACTION definition. If DTB=NO is specified, SYNCPOINT ROLLBACK is treated as a SYNCPOINT and all the updates are committed.

Whenever possible, use the CICS SYNCPOINT or CICS SYNCPOINT ROLLBACK command for committing updates instead of specifying the following CA Datacom/DB commands:

• COMIT
• LOGCP
• LOGTB
• ROLBK

When modifying legacy programs containing these commands, consider converting the LOG commands to SYNCPOINTs at that same time.

Note: CBS and SQL sets are beyond the scope of this document. They are not obligated to follow any of the rules stated in this document concerning exclusive control. There can be cases where sets remain beyond a SYNCPOINT or task termination or log commands.

Leveraging the IBM OTE to Increase Performance

Business Value

Proper use of the Open Transaction Environment (OTE) allows applications to run faster with higher throughput and better performance.

Additional Considerations

Take advantage of many TCBs available in the OTE in CICS to relieve stress on QR TCB. Allow multiple transactions to run simultaneously to achieve higher throughput and better performance.

To leverage the OTE for increased performance:

• Find out whether your application is threadsafe.
• Find out whether your application makes DB2 or other resource manager calls with DATACOM calls.
• Find out whether you are QR TCB bound or CPU bound.
• Find out whether the application provider has a threadsafe version of the code.
• Find out whether your application runs with EXECKEY of CICS or USER.
• Find out the value of MAXOPNTCBS in the CICS initialization phase and whether you can change the value.

All factors play important roles in increasing performance in OTE. Consider them collectively to maximize performance of the application.

OTE provides many OPEN TCBs (engines) where CICS can run its transactions simultaneously. The goal is to achieve threadsafety on as many applications as possible to take advantage of this feature in CA Datacom CICS Services.

To achieve that goal, CA Datacom CICS Services was written and enhanced to threadsafe standards in Version 14.0 to run in the OTE environment. To take advantage of this new feature, select the option OPENAPI=YES in the DBCVTPR macro. The default is OPENAPI=NO which keeps CA Datacom CICS Services running on QR TCB (Quasi-reentrant) like it was in r11. This selection does not necessarily depend on the application threadsafety and can be selected independently. However, the following selection criteria may help you decide.

The environment that benefits most from this selection is one that allows for the use of many TCBs. It is also architected to minimize TCB switching while running a transaction from the start to end.

Example Scenarios

Select a value of YES for OPENAPI if your environment can be defined as:

1. A threadsafe application running.
2. An application with both DATACOM and non-DATACOM resource manager calls such as DB2 regardless of application threadsafety.
3. A clearly defined QR or CPU bound environment regardless of application threadsafety. In this case, the application would keep running on QR but CA Datacom CICS Services would run on L8 TCBs. Monitor the environment and measure performance to help ensure that expected performance improvements have been achieved. Consider changes for application threadsafety if the expected throughput goals have not been achieved.

Monitor your environment and make any necessary changes for performance gains.

If choosing the option OPENAPI=YES has minimal or even negative impact on the performance of the system, it would be a good time to take one of the following actions:

• Replace the application with a threadsafe version.
• Run the application with the EXECKEY=CICS option if possible.
• Increase the number of MAXOPNTCBs in the CICS SIT table. With respect to choosing a proper value for MAXOPNTCB, this value must be set to at least the value of the USERS value in the DBCVTPR. The MAXOPNTCB value must also account for the other resource managers that use open TCBs and all the applications that use open TCBs. This is in addition to the number of MAXOPNTCB for the CA Datacom threads.

Note: See the IBM documentation about selecting a value to accommodate the need of your CICS environment for open TCBs and requirements for the CA Datacom/DB threads.