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News from Tech Support - The HP-UX FAQ

SarCheck will find a few bugs in the sar utility, so here's the FAQ section from the manual. These questions make up 80 percent of our support calls.


Frequently Asked Questions (FAQ):

What am I suddenly getting a message "NOTE: The version number of the agent couldn't be determined"?

Beginning with SarCheck version 7.01.16 for HP-UX, our agent reports on its version number. We compare the agent's version number with that of the analyze9000 program and report on discrepencies. If you're analyzing old data collected with a pre-7.01.16 version of SarCheck for HP-UX, you can expect to see this message and it does not indicate a problem. If it did, the message would be preceded with "WARNING" instead of "NOTE".

Why does SarCheck tell me that my fast new disks are slow?

The speed of disks (as reported by the manufacturer) is usually better than the speed reported by sar. Soft I/O errors, poor locality of reference, and problems with the disk controllers are frequently responsible. Unfortunately, sar doesn't give us enough information to identify the true cause or recommend a solution. If a change to the buffer cache can be useful in circumventing the problem, SarCheck will recommend it.

SarCheck uses the following thresholds when commenting on disk service time:

> 100ms	        Not likely to be a magnetic disk
50 - 100ms	May not be a magnetic disk
25 - 50 ms	Very slow
16 - 25 ms	Somewhat slow
11 - 16 ms	Acceptable
6 - 11 ms	Relatively fast
0.1 - 6 ms	Very fast, possibly solid state or cached

Another problem is that the drivers for aftermarket disk devices may not work correctly with sar. One site reported that sar was showing 15 - 30 millisecond service times for an EMC RAID array that is supposed to be faster than a solid state disk.

Should I implement recommendations which only show up occasionally?

Feel free to try, but implement the regularly occurring recommendations first, since those will address the most frequently occurring problems. If SarCheck occasionally recommends increasing the amount of memory, you should certainly try it. On systems with some extra memory, SarCheck will be able to make additional recommendations that could not be made on systems where memory is “tight”.

Every time I make changes based on SarCheck’s recommendations, it makes more recommendations. Why doesn't it just figure out the correct values for all the parameters?

That’s not how real performance tuning works. There are no “correct” values because tuning is a series of compromises between various system resources. Performance tuning involves a certain degree of trial and error, and gradual change is the only way to do it.

When I try to run sarcheck, I get the message “sarcheck: not found”. What’s wrong?

Check the following:

  • Are you root?
  • Does the sarcheck script really exist? (look for /opt/sarcheck/bin/sarcheck).
  • Is /opt/sarcheck/bin in your PATH variable? (echo $PATH)

Why do I get the odd message "sar: Starting time must be more than ending time" with HP-UX 11.00?

This is caused by a bug in sar. There was a problem with sar's ability to process starting times using the -s option. Since SarCheck uses sar to produce a sar report, you may encounter this bug. To fix it, make a backup copy of the script /usr/local/bin/sarcheck and then search for, and remove the -s$ST text string. If you need assistance with this, let us know.

Why did SarCheck stop producting reports?

There are two common causes of this:

  1. The software has expired. Run '/usr/local/bin/analyze9000' and look for the expiration date at the bottom of the usage text. If you've licensed SarCheck and the expiration date doesn't make sense to you, run 'analyze -s' and send us the output.
  2. The kernel was rebuilt, but the system was not rebooted. After the kernel is rebuilt (frequently to implement a change recommended by SarCheck), sar may have trouble until the system is rebooted. SarCheck can't produce reports if sar isn't working..

Why does the analyze9000 program produce the error message crt0: ERROR couldn't open dld.sl errno:000000002?

This error message is caused by the analyze9000 program looking for dld.sl in /lib. In some operating systems it is located in /usr/lib and this error message occasionally occurs when the operating system is upgraded. We haven't seen this error since 2004 and don't expect to see it again.

How do I change the starting and ending times of the period being analyzed?

You can control the starting and ending times picked by the SarCheck script with the ST and EN keywords in the sarcheck_parms file. Here is a link to the PDF Manual for the SarCheck v7 Parmsfile.

If you use the 'analyze9000' program to produce SarCheck reports, use the -st and -en switches. Here is a link to the PDF Manual for the SarCheck v7 switches

Regardless of whether you run 'sarcheck' or 'analyze9000' to produce a SarCheck report, you should collect data at consistent intervals throughout the monitoring period. By default, sar data is collected every 20 minutes between 8:00 and 18:00 on weekdays and every 60 minutes at other times. Edit the crontab entry which runs /usr/lib/sa/sa1 to make sure that the data is collected at the same intervals during the entire period you wish to analyze.



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