Assign channel system service failed

[Brian Reiter]

Hi Folks,

Got the following interesting return code from a call to $CRMPSC_GFILE_64:

%DEBUGBOOT-W-CHN, assign channel system service request failed.

The process in question does create a lot of file backed global sections, but in this case are we hitting an internal limit imposed by OpenVMS or something else? The message doesn't seem to imply any quota problems.

I can rework the process to use less global sections or rather not create them as file backed - but I would be interested to know what the cause of the problem is so that I can work around it now rather than later :)

The system we are using is a DS10 running OpenVMS 7-3-2 with the VMS732_UPDATE V2.0 patch installed.

regards

Brian

[Ian Miller.]

could you be hitting CHANNELCNT or FILLM?

could the return code be reported incorrectly i.e. are you reporting the code directly after calling the system service or saving it and reporting later?

It may be that the process was trying to load the traceback image to report another problem but could not as the process had ran out of channels

[Wim Van den Wyngaert]

Via google :
http://h71000.www7.hp.com/wizard/wiz_6308.html

[Brian Reiter]

Ian,

More likely channelcnt - checking the documentation put me off modifying this but I may give it a go.

Wim - thanks for the link. As far as I can tell the system isn't leaking channels. Once its up and running very few new channels are assigned.

Are there any side-effects/issues with upping the channelcnt parameter? Its not one I'm familiar with.


cheers

Brian

[Ian Miller. · Accepted solution]

The CHANNELCNT system parameter sets the size of the channel table in every process. As the size of each entry in this table is small (20 bytes on VMS V7.3-1) then setting it to be a largish value (say 4000) is not a big overhead.

[Ian Miller.]

Note its a good idea to make CHANNELCNT a bit (say 20) larger than the largest FILLM quota on your system. This allows for some channels for things other than files.

[Brian Reiter]

Ian, Wim

Thanks for the help. The explanation itself is very useful and a good guide when we finally deliver these systems.


best regards

Brian

[Wim Van den Wyngaert]

May help
http://h71000.www7.hp.com/wizard/wiz_1071.html

Wim

[Ian Miller.]

just to clarify my previous comment
"Note its a good idea to make CHANNELCNT a bit (say 20) larger than the largest FILLM quota on your system. This allows for some channels for things other than files."

should be at least (say 20) larger than largest FILLM.

[Wim Van den Wyngaert]

In fact, Ian, you don't know haw many exe are linked within an exe. So 20 is a good value but it could be 100 too.