Working in Monitor Data Scan Mode

  • Invoke Monitor Data Scan Mode as follows
    • For a disk file: Enter the command 'MONSCAN DISK fn ft fm', specifying at least the file name and file type of the monitor data file which is to be scanned.
    • For a tape file: Enter the command 'MONSCAN TAPE TAPn', specifying the tape unit where the monitor data tape has been mounted and which has previously been attached to your virtual machine.
    • As a pipe stage: See Using CMS Pipelines as Monitor Data Source for more information.
    See the MONSCAN subcommand in the z/VM: Performance Toolkit Reference for a detailed description.

    The same initial performance screen selection menu will be shown which you also see after entering normal performance monitor mode.

  • Select performance data displays in one of the following ways, just as in normal performance monitor mode:
    • Select a screen with the cursor
    • Key in the number of the screen
    • Key in the fast path command for selecting the screen
    and then press the ENTER key.

    You can view the selected display and switch between different performance displays, just as in normal performance monitor mode. Use the Performance Toolkit Subcommands and Screen Layouts chapter in the z/VM: Performance Toolkit Reference for further information on the available commands, but be aware of the restrictions mentioned above (that is, some performance data displays cannot be selected because they are based on data obtained directly from CP control blocks, not from CP monitor records).

  • Use the NEXTSAMP and SKIPSAMP commands for viewing data for another period. Both commands allow specifying a target time so you can skip directly to a period you are interested in. They differ in the actual processing performed during the skip operation:
    • NEXTSAMP will let all the intermediate data be read and processed too, up to and including the first monitor sample with a time stamp which exceeds, or is at least equal to, the target time you specified. This means you will see all the intermediate measurements in the 'by time' log files and that valid averages can be shown for all screens.
    • SKIPSAMP will just skip any intermediate data records up to the first monitor sample with a time stamp which exceeds, or is at least equal to, the target time you specified. This means that none of the intermediate measurements will be shown in the 'by time' log files and you must expect incorrect averages (there are fields where averages are built by adding values from each sample and then dividing by the number of samples, and these will always show incorrect averages after a SKIPSAMP command).