SDA Extension

[Ian Miller.]

I've been playing around with the SDA extension interface (first documented in VMS V7.2) mostly for my own education and entertainment.

My current effort can be found here
http://eisner.encompasserve.org/~miller/pwait$sda.zip

This is an attempt to analyze a waiting process e.g for use when looking at a hung process.

Do people think something like this would be of use? I'm wondering if I should expand it (I probably will anyway just for fun), tidy it up and make it publicly available.

[Martin P.J. Zinser]

Hi Ian,

builds and installs cleanly on 7.3-2. Also works fine on initial, superficial testing. Still waiting for a hung process to really test it ;-) If you ask me, it definitly looks promising.

Greetings, Martin

[Uwe Zessin]

Ian,
I have not looked at it - does it work on the running system, a dump or even both?

If it works only on the running system - I think it would be easier not to bother with SDA, right? Well, you said you did it for your on fun, so this is OK with me ;-) If it works on both - hey, that's definitely a good idea!

[Peter Hofman]

Nice!
Work also on dumps (tried it on 7.3-1).
I am missing a /ID qualifier. Right now you always have to do:
SET PROC/ID=... before using PWAIT.

[labadie_1]

You could have a look at http://www.pi-net.dyndns.org/jfp/french/

and download sda_extension.zip

I am afraid mwait is the same as yours :-)

[Ian Miller.]

thanks fr the pointer to JFP's SDA_EXTENSION. One of the reasons for postin the question was I had not seen anyone using this interface outside of HP and wished to talk to other people working in this area.

It is very much a work in progress. I wrote it for my own fun partially to explore the SDA Extension interface, partially inspired by a old program called MWAIT and partially prompted by the 'Troubleshooting Hung Processes' session at the bootcamp. It then occured to me that it may be useful as well :-)

It works on crash dumps and the running system. The idea being it does the basic checks to determine what the process is waiting for. It is either an aid for an experianced person to do the basic stuff so to get on to the more intersting stuff or parhaps an aid to a less experianced person.

Re Peter's comment on having to set the process first - this was deliberate however I may add an optional paramter of a process ID to specify the process.

As it seems there is some public interest then I will make it available (when its a bit more complete). Development snapshots may appear on the web site referenced above. I've just uploaded last nights version in which I added the code to get the process channel table with the intent to look at the state of the current I/O.

[labadie_1]

Yes it would be very useful.

I guess you have already seen sys$examples:mbx$sda.c , which is well commented

[Ian Miller.]

I've updated pwait$sda and the updated version is at

http://eisner.encompasserve.org/~miller/

It is still a work-in-progress but I thought I would ask for feedback here as to what to do next. If you look at the source there are various comments giving my thoughts of what other information could be displayed.

Another general idea was to define symbols for the addresses of data recently displayed (like SDA defines PCB, PHD etc). I thought parhaps of defining CCB or parhaps CCB1, CCB2 etc when displaying channel information. These symbols could be used in futher SDA commands.

Another area not yet explored is timer request entries - the TQE list. I'm aware this changed in V7.3-1 from a simple linked list to some sort of tree structure. There is a SHOW PROCESS/TQE command in SDA from V7.3-1

Any comments post here or email to miller at encompasserve dot org

[Ian Miller.]

Now available at

ftp://ftp.process.com/vms-freeware/fileserv/pwait$sda.zip
http://vms.process.com/ftp/vms-freeware/fileserv/pwait$sda.zip

ftp://ftp.tmk.com/vms-freeware/fileserv/pwait$sda.zip
http://www.tmk.com/ftp/vms-freeware/fileserv/pwait$sda.zip

and submitted for the next vms freeware CD.

comments to the email address given in the kit.