Collecting MONWRITE Data:
About as Simple as I Can Make It

This is a simple set of instructions for collecting CP Monitor data via the utility program called MONWRITE.

The CP Monitor settings cited here are useful for problem diagnosis on small to moderately sized systems:

  • MONDCSS is 8192 pages (aka 32 MB)
    • 2048 pages for event data
    • 6144 pages for sample data
      • 3072 pages for sample config records
  • All the cool domains are enabled
  • Samples every 1 minute

In these instructions, you should skip steps marked (skip) if your z/VM system is already running a performance monitoring tool such as z/VM Performance Toolkit or some third-party package. In such a case the monitor data you collect will be according to the Monitor settings said tool already established.

Follow these simple instructions:

  1. (skip) Log onto the user called MAINT.

    1. Define the MONDCSS segment. These commands will define a 32 MB DCSS (x'2000' aka 8192 pages) at the 160 MB line. CP DEFSEG MONDCSS A000-BFFF SC RSTD CP SAVESEG MONDCSS

    2. Let's start with a clean slate for CP Monitor. CP MONITOR STOP

    3. Under MONITOR EVENT, collect all domains except SEEKS and SCHEDULER. CP MONITOR EVENT ENABLE ALL CP MONITOR EVENT DISABLE SEEKS ALL CP MONITOR EVENT DISABLE SCHEDULER ALL

    4. Under MONITOR SAMPLE, collect all domains and set aside 3072 pages for config records. CP MONITOR SAMPLE ENABLE ALL CP MONITOR SAMPLE CONFIG SIZE 3072

    5. Set Monitor's sample intervals. CP MONITOR SAMPLE RATE 1 SEC CP MONITOR SAMPLE INTERVAL 1 MIN

    6. Then start CP Monitor, allowing 2048 pages for event data. CP MONITOR START PARTITION 2048

    7. Log off of MAINT.

  2. Log onto the user called MONWRITE.

    1. Find yourself a filemode letter suitable for holding the collected data. To find one, issue the command QUERY DISK and look for the R/W filemode that has the most free blocks. In the example below, filemode A is the only R/W filemode and it has 53989 free blocks. identify MONWRITE AT GDLBPRF3 VIA RSCS 04/20/20 09:39:10 EDT MONDAY Ready; T=0.01/0.01 09:39:10 query disk LABEL VDEV M STAT CYL TYPE BLKSZ FILES BLKS USED-(%) BLKS LEFT BLK TOTAL MON191 191 A R/W 300 3390 4096 0 11-00 53989 54000 MNT190 190 S R/O 207 3390 4096 696 18866-51 18394 37260 MNT19E 19E Y/S R/O 500 3390 4096 1120 35822-40 54178 90000 Ready; T=0.01/0.01 09:39:15 Let's pretend you looked and discovered filemode A to be the desired target.

    2. Run the MONWRITE program, collecting to the filemode letter you identified. The example below writes the collected data to file MYDATA MONDATA A. MONWRITE MONDCSS *MONITOR DISK MYDATA MONDATA A

    3. After, say, 30 minutes, type MONWSTOP. This stops collection.

    4. Package and send us the MONWRITE file. For instructions, read this.

    5. Erase your MONWRITE file. ERASE MYDATA MONDATA A

    6. Log off of MONWRITE.

  3. (skip) Log onto the user called MAINT.

    1. Stop the monitor. CP MONITOR STOP

    2. Log off of MAINT.