Siemens U3585-J-Z125-8-76 1 Monitoring cycle, Online monitoring cycle, SM2 Measurement Status

SM2 monitoring program Monitoring cycle

2.7 Monitoring cycle

As mentioned above, SM2 collects data at regular intervals known as monitoring cycles (except for the monitoring programs DISK and TASK). At the end of each monitoring cycle, the processed data is written to the data buffer and to the SM2 output file, if one is available. The length of the monitoring cycle is preset at 150 seconds when the subsystem is started. The SM2 administrator can change this setting using the OFFLINE-PERIOD operand of the MODIFY-MEASUREMENT-PERIODS statement. The value is entered under OFFLINE PERIOD in SM2 MEASUREMENT STATUS .

Online monitoring cycle

The online cycle also defines a monitoring cycle in which the monitored data for online analysis is collected and written to another buffer. The online cycle is deactivated by default. It can be modified using the ONLINE-PERIOD parameter in the MODIFY-MEASUREMENT- PERIODS statement. When the online cycle is deactivated, the ONLINE-PERIOD corre- sponds to the OFFLINE-PERIOD. The CYCLE column in each report shows the online value currently set. In addition, the value under the ONLINE-PERIOD column is entered in

SM2 MEASUREMENT STATUS.

The online cycle should only be activated if the delay at the terminal is too great when carrying out online monitoring. This may happen if a long monitoring cycle is set for output to an SM2 output file. Please note that by activating the online cycle, you also increase the workload on the system.

Sampling cycle

For monitored-data acquisition based on random sampling, SM2 subdivides the monitoring cycle into a large number of small, regular time slots called sampling cycles. The monitoring task is activated at the specified interval for data collection. At the end of each sampling cycle, snapshots are taken for some variables. From the large number of snapshots, a mean value is computed for each monitoring cycle.

The accuracy of the computed value thus depends on the length of the sampling cycle:

The shorter the sampling cycle, the greater the number of snapshots that can be taken during the monitoring cycle. The SM2 workload on the system, however, increases simul- taneously.

The sampling cycle is preset to 800 milliseconds when the subsystem is started.

The SM2 administrator can change this value in the SAMPLING-PERIOD operand of the MODIFY-MEASUREMENT-PERIODS statement. The SAMPLING PERIOD column in the SM2 MEASUREMENT STATUS indicates the current setting, while the SAMPLES column in the individual reports contains the number of samples taken during the latest monitoring cycle.

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