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Disks statistics for one day

Frequent Advisor

Disks statistics for one day

Hi All,

Could you please help, how can i find the disks statistics for one day.
I tried "monitor disk/per" options to get this data but need to monitor whole day and get the screen shot every one hour and find the average values.

Is there any other efficent way to find this statistics from VMS(OpenVMS 8.3) commands.

Steven Schweda
Honored Contributor

Re: Disks statistics for one day

Define "statistics".

Do "SHOW DEVICE /FULL device" every hour?

Jon Pinkley
Honored Contributor

Re: Disks statistics for one day

What type of statistics are you looking for? Space utililation, number of i/o operations/period or how long operations are taking.

T4 will collect a lot of info and give you the opportunity to review it at a later point in time.

But first, you need to decide what you are really trying to measure. "A screen shot every one hour". does that mean an average of the last hour, or a 3 second sample once an hour. Those will give quite different results.

I had to look up what "monitor disk/per" does.

$ help monitor monitor disk /percent





/NOPERCENT (default)

Controls whether statistics are expressed as percent values in
display and summary outputs. The /PERCENT qualifier is applicable
only to the DISK, MODES, SCS, and STATES classes.

It is not clear to me what this is really measuring. Percent of what?
it depends
John Gillings
Honored Contributor

Re: Disks statistics for one day

Try this:


Or, in a batch job:


In both cases you can view the log file at any time. Pages are written at 1 hour intervals and finish 24 hours after starting. Averages are accumulated.

What I'm not sure about is the granularity. If it's just a single point sample every hour, that might not be what you're after.

T4 gathers disk statistics. Have you tried it?

A crucible of informative mistakes
Hein van den Heuvel
Honored Contributor

Re: Disks statistics for one day

I like T4 for that kind of work.
Just google for OpenVMS and T4 and start reading.

A very very quick way to get per disk stats over a period of time is to use:


If you want daily or hourly, then take a snapshot every so often and SUBTRACT the counters and times to get a rate.
If you opt to do this in DCL, then be sure to watch out not to exceed 32 bit integers.


Hope this helps some,
Frequent Advisor

Re: Disks statistics for one day

I need the disk statistics in terms of disk performance like detect IO bottleneck and other parameters(if available).

i want to give data which will show the disk performance (not sure which are parameter will decide).

Thanks in advance.

Frequent Advisor

Re: Disks statistics for one day

Is there any way to find the bottleneck for disk in system?

Kindly let me know if you want any more information to help me on this.Thanks
Wim Van den Wyngaert
Honored Contributor

Re: Disks statistics for one day

If you have performance advisor, you can watch the number of IO's, the thruput in MB, the aueue length and the size of the IO's.

A bottleneck is difficult to detect because stuff like Sybase or backup will do the maximum of IO's on purpose. It also depends on the hardware used. You can e.g. monitor disks on a HSG80 itself.

Hein van den Heuvel
Honored Contributor

Re: Disks statistics for one day

>> Is there any way to find the bottleneck for disk in system?

Yes. You start by droppping all assumptions (such as a disk being the bottleneck at all)
Then you observe the system and 'see' where it hurts. Some stuff is easy, like 100% CPU usage. But network and disk may be much more tricky due to parallel versus serial activities, asynchronous versus synchroneous, forced serialization using locking (RMS bucket locks)
For mere money I'll come over explain!

Seriously, you may want to try to work with a consultant who has done this before to get up to speed in this area.

I kinda read your initial topic question wrong forcussing on "disks statistics for one day.". That is way too coarse. It will hide any and all bottlenecks.
"get the screen shot every one hour and find the average values."

That is still too coarse, and too impractical.

Now capture every second or every 10 seconds for the critical business hours and REPLAY with and interval of an hour as you please, and tighten the start, end and interval as you learn more.
Something like:

$ moni disk/inter=1/record=disks.tmp/nodisp/end=...

and later, at your leisure...

$ moni disk/inter=300/input=disks.tmp/view=5

But please just get T4 / TLVIZ ( or any other of the several ready made tools ) and let it do all of that for your!
by sure to check out CSVPNG which will allow you to automate extracting T4 and find min, max, averages... even tell you when it worst time was.

If you are seriously studying disk performance, be sure to ask the help from the XFC extension to ANALYZE/SYSTEM.
and many more.

If for some reason you want to hand craft something you using snapshots as I suggested earlier, then find below some PERL code to get you going. It is a reduced version of a larger script i sometimes find I need.
The script is appended below. Sample output:

$ show memory/cach=volum=*/out=a.tmp
$ wait...
$ show memory/cach=volum=*/out=b.tmp
$ perl show_cache_by_volume.pl a.tmp b.tmp
Sample time is 35280 seconds

Disk Virtual reads Read hits Virtual writes
_$1$DGA1: 201230 5.7 197148 5.6 19213 0.5
_$1$DGA1: 201230 5.7 197148 5.6 19213 0.5
_EISNER$DKA0: 99661 2.8 89353 2.5 2138 0.1
_EISNER$DKA0: 99661 2.8 89353 2.5 2138 0.1

Good luck!
Hein van den Heuvel ( at gmail dot com )
HvdH Performance Consulting

$ type show_cache_by_volume.pl
use strict;
use warnings;
use Time::Local;

my (%old, %new, $name, $disk, $counter, $dif, @disks, @counters);

# -- get data

@counters=('Virtual reads', 'Read hits', 'Virtual writes');
$name = shift or die "Please provide an OLD file:";
&read_file (\%old, $name);
$name = shift or die "Please provide an NEW file:";
&read_file (\%new, $name);

# -- process and output

my $seconds = $new{Seconds} - $old{Seconds};
printf "Sample time is $seconds seconds\n\n";
printf "%15s %20s %20s %20s\n", 'Disk', @counters;
for $disk (sort @disks) {
my $line = sprintf "%15s", $disk;
for $counter (@counters) {
$dif = $new{$disk.$counter} - $old{$disk.$counter};
$line .= sprintf (" %9d %7.1f", $dif, $dif/$seconds);
print $line.qq(\n);

# --- done.

sub read_file {
my ($array, $name) = @_;
open FILE, "<$name" or die "Could not open file $name.\n$!";
while () {

if (/^\s+Sys.* on\s+(\d+)-(\w+)-(\d+)\s+(\d+):(\d+)/) { # Time stamp line?
$$array{Seconds} = timelocal(0,$5,$4,$1,$n-1,$3-1900);

if (/^(_\S+:)\s+/) { # Disk & volume line ?
$disk = $1;
push @disks, $disk;
next unless /\d$/; # Line ends in a number ?
for $counter (@counters) { # a number we care for ?
$$array{$disk.$counter} = $1 if /$counter\s+(\s\d+)/;
Richard W Hunt
Valued Contributor

Re: Disks statistics for one day

Concur that a pre-made solution is WAY far preferred than rolling your own, but here is an overview of how to do that.

You can set up batch jobs to run the MONITOR DISK/ITEM=xxxx command (xxx=ALL, QUEUE, or OPERATION) and capture the output to a binary file. At the end of your period of performance, you can then replay the captured data to a file in a text format. Now comes the fun part.

Read that text file, DCL is as good as any other thing for prototyping. The top of each page tells you the node and time of sample. After that date/time line, the next nonblank line tells you what wes monitored on that page. Then you get the list of disks and the CUR, AVG, MIN, and MAX - in predictable columns! So extract the values and reformat to have device, timetag, and current value in another file.

Eventually you can get to a file with a date & time stamp, device name, parameter name, and observed value. Which you can then export to something like EXCEL or any other package that has built-in graphic abilities. From there, you are on your own as to what you wanted to see.

This is what I used to call the "poor man's SPM" (after the old System Performance Monitor software that used to be standard on older versions of VMS). Is it elegant? NO. Is it easy? Not that hard, just tedious. Does it work? Most of the time. If you take this approach, build in some robustness to handle unexpected things like broadcast messages or newmail messages that might show up in the output stream.

Good luck!
Sr. Systems Janitor