Siemens U3585-J-Z125-8-76 1, SM2 monitoring system manual Acquisition of monitored data

SM2 monitoring program Acquisition of monitored data

2.6 Acquisition of monitored data

SM2 records a wide range of monitored data and outputs it to either a screen and/or a file. The data is collected at regular intervals, called monitoring cycles. Some of the monitoring tasks are carried out by default, while others are carried out by special monitoring programs which can be activated as and when required.

The monitored data is then processed and displayed internally by SM2 or by independent SM2 monitoring and analysis routines.

There are three methods of collecting data:

●Based on the monitoring cycle

Most of the monitored data (e.g. the CPU load) is collected at the end of each monitoring cycle. The current count (or time stamp) is taken from the SM2 or system tables, and the difference between this value and the value at the end of the last monitoring cycle is calculated.

The same procedure is used to calculate the intermediate values for the methods described below at the end of the monitoring cycle (except for the monitoring programs DISK and TASK).

A monitoring cycle can be set to between 10 seconds and 1 hour.

●Based on the sampling cycle

Because the status is constantly changing, it may not be appropriate to wait until the end of the monitoring cycle to query some monitored data (e.g. device utilization). When acquiring this type of monitored data, it is recommended that the monitoring cycle be broken down into several sampling cycles. At the end of each sampling cycle, the current monitored variable is obtained. Then, at the end of each monitoring cycle, the mean value across all sampling cycles is computed.

A sampling cycle can be set between 200 milliseconds and 10 seconds.

●Event-driven

Some monitored data (e.g. the distribution of disk operation times) is determined by monitoring events within the system. When an event occurs, such as the start of an input/output operation, an SM2 routine is activated which collects the event-specific data. This data is then used to calculate the monitored variables.

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