Summary of performance monitoring tools

During the benchmark measurement periods, the following tools are used:

RMF Monitor I

IBM RMF Monitor I records system resource usage, including CPU, DASD, and storage. It is also used with the workload manager (WLM) configuration to record the CPU, transaction rates, and response times for CICS service classes and report classes.

SMF records 70 - 79 are written on an interval basis. They can be post-processed by using the ERBRMFPP RMF utility program.

RMF Monitor III

RMF Monitor III records the coupling facility activity for the logger and temporary storage structures.

SMF records 70 - 79 are written on an interval basis. Also, the records can be post-processed by using the ERBRMFPP RMF utility program. RMF Monitor III can be used on an interactive basis and the data can be written to VSAM data sets for later review.

CICS TS statistics

CICS statistics are used to monitor and report CICS resource usage, including CPU, storage, file accesses, and the number of requests that were transaction-routed.

With CICS interval statistics, most of the counters are reset at the start of the interval so that any resource consumption that is reported relates only to the observed measurement period. Interval statistics can be activated by using the CEMT SET STATISTICS command. However, when you set this interval, the first interval can be adjusted to a shorter time so that all the intervals are synchronized to the STATEOD parameter. For example, if you use CEMT to set the interval to 15 minutes at 10 past the hour, the first interval expires in 5 minutes so that all future intervals line up on 15-minute wall clock boundaries. The values in this first report also can be associated with a much longer period, depending on the time of the last reset.

Another alternative to the use of interval statistics is to use CEMT to reset the counters and then at the end of the measurement period, use CEMT to record all the statistics. Resetting the statistics requires a change of state from ON to OFF or from OFF to ON. To ensure that this change happens, the following commands provide an example of resetting the statistics in one CICS region: 

F CICSA001,CEMT SET STAT OFF RESET

F CICSA001,CEMT SET STAT ON RESET
The measurement period is between the RESET and the RECORD, as shown in the following example:

F CICSA001,CEMT PERFORM STAT ALL RECORD

Regardless of whether the statistics are ON or OFF, when a PERFORM STAT ALL RECORD command is issued, a statistics record is written.

CICS statistics are written as SMF 110 subtype 2 records. They can be post-processed by using the CICS statistics utility program, DFHSTUP, or CICS Performance Analyzer.

CICS TS performance class monitoring

When CICS performance class monitoring is turned on by using MNPER=ON in the CICS startup parameters or CEMT or CEMN transactions to turn it on dynamically, a performance class monitoring record is generated for every executed transaction when the transaction ends.

The following command is an example of turning on CICS performance class monitoring and resource class monitoring in one CICS region:

 F CICSA001,CEMT SET MON ON PER RESRCE
Monitoring can then be turned off by using the following command: 
F CICSA001,CEMT SET MON ON NOPER NORESRCE

The performance class record of each transaction contains information about the resources that were used by that transaction, how much CPU was used on all the various task control blocks (TCBs), and information about how long it waited for different resources. Resource Class Monitoring records contain information about the individual files, temporary storage queues, and distributed program links (DPLs) that were used by transactions.

Monitoring records are written as SMF 110 subtype 1 records that can be analyzed by using CICS Performance Analyzer.

Hardware instrumentation counters and samples

The CPU Measurement Facility (CPU MF) is described CPU Measurement Facility. The CPU MF capability is built into the hardware, and a z/OS component called hardware instrumentation services (HIS) sets up buffers that the hardware then uses to store the sampling data. When a number of buffers are filled, the hardware generates an interrupt. This interrupt enables HIS to asynchronously collect the sampling information and save it to a file in the z/OS UNIX file system. It also provides the ability for the samples to be gathered without the software responsible for collecting the data, having to run at the highest Workload Manager priority level.

HIS can be used to collect the following types of data:
  • Counters
  • Instruction samples

HIS counters are written as System Management Facilities (SMF) 113 records and to the z/OS UNIX file system. These counters contain information about key hardware events, such as the number of instructions that are executed, the number of cycles that were used, and the amount of instruction cache and data cache misses. Counters are used to provide a high-level understanding of how the address spaces interact with the hardware.

HIS instruction samples are written only to the z/OS UNIX file system. The samples are used to provide a view of CPU activity for individual instructions or groups of instructions. Tools enables the inspection of this data to help the IBM CICS performance team understand where hot spots exist in the CICS runtime code. Hot spots are short sequences of 1 or 2 machine instructions that consume a disproportionately large fraction of the total CPU cost. These hot spots are frequently caused by data access patterns that do not make optimal use of the hardware cache subsystem. Tooling that is written to consume HIS instruction samples also allows the comparison of two benchmark runs, where differences in performance can be analyzed at the instruction level.

For more information about configuring and the use of HIS, refer to Setting Up and Using the IBM System z CPU Measurement Facility with z/OS, REDP-472.