sysgen parameter CHANNELCNT not getting changed

[Srikanth Arunachalam]

Hi,

I need to set the value of CHANNELCNT sysgen parameter to a larger value. I perform the following :-
mc sysgem
SYSGEN> USE CURRENT
SYSGEN> USE ACTIVE
SYSGEN> SET CHANNELCNT 2048
SYSGEN> WRITE CURRENT
SYSGEN> WRITE ACTIVE
SYSGEN> EXIT

Is this not a dynamic parameter. I dont see the change in sys$system:params.dat. Please let me know how to make this change permenant.

Thanks,
Srikanth

[Thomas Ritter]

$mc sysgen
use current
show channelcnt

This will show the value.

Then reboot.

[Andy Bustamante]

Hi Srikanth,

First a few usage notes:
USE CURRENT opens the current parameter file on disk, sys$system:alphavmssys.par for Alphaservers. This is how your system will be configured following the next reboot. Following the next boot, CHANNELCNT should be set to your new values.

USE ACTIVE uses the live system parameters. This is what what your system is running right now.

Although you can set system parameters with SYSGEN, it's not recommended. You should edit sys$system:modparams.dat and add a line like one these:

CHANNELCNT=2048 ! comment date/reason
MIN_CHANNELCNT=2048 ! comment date/reason

Then use SYS$UPDATE:AUTOGEN.COM.

@sys$update:autogen savparams testfile

Review the report file, agen$params.report for warnings, errors, cautions.

Then

@sys$update:autogen setparams (reboot)

MODPARAMS.DAT is the recommended way to make changes and not have a future autogen overwrite your changes. At the very least add the new value for CHANNELCNT to spare some one down the line form having to document changes before tuning the system.

Chapter 1 of the System Manager's vol 2 goes into much more detail. See http://h71000.www7.hp.com/doc/82FINAL/aa-pv5nj-tk/aa-pv5nj-tk.HTMl.

Before you start anything, I'd also recomment creating a copy of the parameter file, sys$system:alphavmssys.par, vaxvmssys.par or ia64vmssys.par.

Andy

[Morcos]

Hi Srikanth,

The params.dat file is created from the getdata phase.During this phase, autogen is getting data from the 3 inputs to autogen and putting them in the params.dat file.

In your case you are not using autogen, you are using sysgen:
to determine if a parameter is dynamic or static you should:
SYSGEN> SHOW CHANNELCNT , if there's a D so it's a dynamic and if no D it's static.

I think that CHANNELCNT is not dynamic , it's a static parameter and the system requires reboot.

also
SYSGEN> WRITE CURRENT , you are saving to alphavmssys.par(alpha server) and not to params.dat.

Hope this helps.
Ziad

[Srikanth Arunachalam]

Hi,

Thanks for your response. I will modify them and give a reboot of the system.

Many thanks,
Srikanth

[comarow]

As a comment.

Channelcnt effects other paraments, and
really should be changed via autogen.

That said, if you want to just change
it, then I'd recommend also setting
it in modparams.dat so that when Autogen
does get run you won't lose your changes.

Bob C

[Srikanth Arunachalam]

Thanks everybody for your response. This parameter is now set.

Regards,
Srikanth

[comarow]

I should have added it.

You should not be saying USE active or Write Active.

[Srikanth Arunachalam]

Hi,

Can you please explain me the specific context you were saying not to use the command. Otherwise, I have managed to set it using modparams.dat already.

Thank you.

Srikanth A

[Andy Bustamante · Accepted solution]

> USE ACTIVE
> changes
> WRITE ACTIVE

This sequence will modify the current system parameters in use. It will not be saved for the next boot. For dynamic parameters this is sometimes useful to avoid rebooting. For a paremeter like CHANNELCNT which requires a reboot this doesn't do anything.

> USE CURRENT
> changes
> WRITE CURRENT

This modifies the system parameters for the next reboot. Changes here are generally considered "fast and dirty." You can manage a system like this, however anyone following you is going to have problems.

Using AUTOGEN and the modparams.dat file allows you to provide a list of system modifications documented. Autogen uses this list, checks for releationships and will provide warnings in the AGEN$PARAMS.REPORT file. You can review this file, modify your modparams and rerun AUTOGEN. AUTOGEN tunes the "average system" and collects feedback from your environment. Your application and users may have additional requirements. The MIN_ and MAX_ prefix allow you to set boundries.

It's not unusual to run autogen, collect data for a few days, or over the "end of quarter" and rerun autogen. Pick your peak periods and tune around those.


Andy

[Jan van den Ende]

Srikanth,

not claiming that our way is the best there is, but here it is anyway:

Each week we run AUTOGEN SAVPARAMS GETDATA at peak time (for most load) on each cluster node (from a scheduled batch job)
Next evening, when the systems tend to be quieter, we run AUTOGEN GENPARAMS SETPARAMS FEEDBACK, generating AGEN$REPORTs in the process.
Next morning we review those reports, and if a trend approaches criticallity we schedule a reboot.
If you are aware of trends, you can prognose values (especially for non-dynamic params) and enter MIN_ or MAX_ values in MODPARAMS, such that reboot needs become rarer and rarer.
Do not expect, nor aim, to get there in one pass!

hth

Proost.

Have one on me.

jpe

[Srikanth Arunachalam]

Hi JPE

Many thanks as usual JPE for your response and this forum has been really good and quick in responding to queries.

Many thanks to everyone and will close the thread with this note.

Regards,
Srikanth

[John Gillings]

Srikanth,

(late response)...

Please be VERY CAREFUL using SYSGEN!

>> SYSGEN> USE ACTIVE
>> SYSGEN> SET CHANNELCNT 2048
>> SYSGEN> WRITE CURRENT

This sequence is very dangerous. You've taken your ACTIVE set and written it back to CURRENT. In many cases that may be benign, but there are a few situations where it could result in an unbootable system. At the very least, you don't know if you're committing some dynamic changes to other parameters since the last reboot to the permanent set.

Please make sure you know EXACTLY which set of parameters you're working with. Personally, I ALWAYS type an explicit USE command in SYSGEN to be certain. Most of the time it would be:

SYSGEN> USE ACTIVE
SYSGEN> ... change some dynamic parameters
SYSGEN> WRITE ACTIVE

OR

SYSGEN> USE CURRENT
SYSGEN> ... change some permanent parameters
SYSGEN> WRITE CURRENT

For permanent parameters, you're MUCH better off making your changes in MODPARAMS and using AUTOGEN to implement them. Changes should document what was done, when, why and by whom. You're also better off using a MIN, MAX or ADD, so that AUTOGEN can take other factors into consideration. Your CHANNELCNT change should look like this in MODPARAMS.DAT:

MIN_CHANNELCNT = 2048 ! Srikanth 27-Oct-2006, required by

[Srikanth Arunachalam]

Hi John,

Thanks for your precise answer. I will follow this when I am changing it for the next time.

Thanks,
Srikanth A