gtpo1mhpOperations

Online Data Collection

The online data collection utility gathers detailed and summary performance data on the real-time data collection tape (RTC). You can run 4 different collectors to gather this performance data:

Collector
Description

File collector
Collects file and virtual file address (VFA) performance data.

Message collector
Collects message performance data for resources that are defined to the TPF system when the data collection utility is started.
Note:
Message performance data is not collected for resources that are defined to the TPF system after the data collection utility is started.

Program collector
Collects program performance data.

System collector
Collects a cross section of system performance data.

Use the ZMEAS commands to start, stop, and restart online data collection.

Starting Data Collection

You can run data collection in 2 different modes: continuous mode and sampling mode.

Continuous Mode

In continuous mode, all 4 of the collectors are run one after the other to gather summary performance data, and then one collector is run for a specified interval of time to collect detailed performance data. This collection interval is repeated 300 times, which is the default defined by INTVL in DATACO. For example, you can run the system collector in continuous mode and specify that it is run for 5-second intervals. These collection intervals are repeated 300 times for a total of 1500 seconds, or 25 minutes.

Sampling Mode

In sampling mode, both summary and detailed performance data are gathered by one or more specified collectors, in turn. These collectors are run one after the other in a specified order for specified collection intervals. You determine if the collection intervals for the different collectors are the same. After the specified collectors are run for the specified collection intervals, 1 collection cycle is complete. A gap, which you define (and is at least 3 seconds long), follows each collection cycle. Together, the collection cycle and the gap make up a sampling period. This sampling period is repeated again and again for a specified length of time.

For example, you can run the system collector and the message collector in sampling mode. If you specify that the collection interval for the system collector is 20 seconds, the collection interval for the message collector is 15 seconds, and the sampling period is 40 seconds, the length of time for the collection cycle is 35 seconds (20 seconds + 15 seconds) and the length of time for the gap is 5 seconds (40 seconds - 35 seconds). If you specify an overall length of time of 8 minutes (480 seconds), the sampling period is repeated 12 times (480 seconds ÷. 40 seconds).

Specifying How Many Events to Sample

The file and program collectors gather detailed performance data by sampling file and program events. These events can occur very frequently; so frequently, in fact, that the resulting volume of performance data can be a problem. To control the volume of data, you can specify how many events the file and program collectors sample. For example, these collectors can sample every event or every other event.

When you specify this value using the ZMEAS command, you actually specify the number of events to skip. That is, if you want the file and program collectors to sample every event, you specify that you want to skip 0 events. If you want these collectors to sample every other event, you specify that you want to skip one event. By default, the file and program collectors skip every 99 events.

It may be easier to think about the number of events that are skipped in terms of a percentage. For example, data collection can skip 50% of the events or it can skip 99% of the events. The following table provides some common percentages for the corresponding skip factor.

Percentage Skip Factor Description
0% 0000 Do not skip any events.
50% 0001 Skip every other event.
75% 0003 Sample an event, and then skip 3 events.
80% 0004 Sample an event, and then skip 4 events.
90% 0009 Sample an event, and then skip 9 events.
99% 0099 Sample an event, and then skip 99 events.
99.9% 0999 Sample an event, and then skip 999 events.
99.99% 9999 Sample an event, and then skip 9999 events.

If you know the percentage of events that you want to skip and need to determine the skip factor, use the following formula:

    skip = (percentage ÷. (100 - percentage))
 

For example, the skip factor for 80% is determined as follows:

    skip = (80 ÷. (100 - 80))
    skip = (80 ÷. 20)
    skip = 4
 

If you know the number of events you need to skip and want to determine the percentage, use the following formula:

    percentage = (skip ÷. (skip + 1)) × 100
 

For example, the percentage for a skip factor of 3 is determined as follows:

    percentage = (3 ÷.(3 + 1)) × 100
    percentage = (3 ÷. 4) × 100
    percentage = (.75) × 100
    percentage = 75
 

To Start Data Collection

  1. Enter the ZDSYS command to verify that the TPF system is above 1052 state and not cycling.
  2. If the TPF system is not above 1052 state, enter the ZCYCL command to change to the appropriate system state.
  3. Enter the ZTVAR and ZTMNT command to mount an active RTC tape.

    You may also want to mount a standby RTC tape if data collection will be running for a long period of time or if there is a significant amount of system activity. You can mount the active or standby RTC tape as blocked or unblocked.

  4. Enter the ZMEAS command to start data collection. See ZMEAS-Start Data Collection for more information about the ZMEAS command.

Stopping Data Collection

Data collection stops automatically and dismounts the RTC tape after the duration you specified in the ZMEAS command is reached. In continuous mode, the duration is equal to the time interval you specified multiplied by the value of INTVL, which is 300 by default. In sampling mode, the duration is equal to the number of minutes you specified.

You can also enter the ZMEAS END command to stop data collection before this duration is complete. If you enter the ZMEAS END command while data collection is running in continuous mode, data collection is not stopped until after the current time interval is completed. If you enter the ZMEAS END command while data collection is running in sampling mode, data collection is not stopped until after the current sampling period is completed.

See ZMEAS END-End Data Collection for more information about the ZMEAS END command.

Restarting Data Collection

If a catastrophic system error occurs while data collection is running and you perform an initial program load (IPL) for the TPF system, do the following to restart data collection:

  1. Enter the ZTOFF command to dismount the RTC tape.
  2. Enter the ZTMNT command to mount the RTC tape again.
  3. Enter the ZMEAS command to start data collection again.
Note:
Do not use the performance data gathered before the system error occurred.

If a non-catastrophic system error occurs while data collection is running, you may need to enter the ZMEAS RESET command to clear the residual status before you can start data collection again. In this case, do the following:

  1. Enter the ZMEAS RESET command to reset data collection. This function automatically dismounts the RTC tape.
  2. Enter the ZTMNT command to mount the RTC tape again.
  3. Enter the ZMEAS command to start data collection again.

Enter the ZMEAS RESET command only in place of a ZRIPL command. Do not enter the ZMEAS RESET command to reset data collection if data collection stalls because the system task dispatcher is shut down.