Full Thread Dump - what caution should be used ?

[Former Member]

Dear All,

Whe had a crash on our system recently and one of the answer we received so far from SAP, was that this crash was caused by a Full Thread Dump (FTD)

I don't want to go in full detail of what were the consequences that this FTD caused, but to put it simple - the whole FTD was taking more than 13 min to conclude... and then the whole system colapsed.

SAP recommends to issue the FTD with caution.

But the question is - what type of caution ?

As an administrator, and if the system seems unstable, I need to be quick triggering FTD to be able to "see" what is wrong with the system, what is consuming resources, etc...

Thus a FTD is vital in this type of situations.

WIthout it we are blind.

So my questions are:

1) What impact does a Full Thread Dump has on the system ?

2) And if it has high impact u2013 what alternatives do we have to access the

necessary logs to help us troubleshooting admin issues ?

3) Does SAP has any recommendation regarding triggering full thread-dumps ?

4) And last, but not least, is it normal for a full thread-dump to last 13

minutes ?

Kindest Regards

/Ricardo Quintas

[anja_engelhardt2 · Accepted solution]

Hello Ricardo,

I'll try to answer your questions:

1) What impact does a Full Thread Dump has on the system ?

--> normally a full thread dump takes some seconds in maximum. It's not done by SAP software but by the JDK itself. As it scans the whole java memory the system may be slow during the time the thread dump is written.

2) And if it has high impact u2013 what alternatives do we have to access the

necessary logs to help us troubleshooting admin issues ?

--> it depends on the issues. Thread dumps are only helpful in case of a system freeze. For all other problems normally it's not helpful. Take a look at the log files in server/log directory and work. This helps in most cases - especially for admin issues.

3) Does SAP has any recommendation regarding triggering full thread-dumps ?

--> Yes - in case of a system standing still without reaction. With the help of a thread dump a deadlock can be identified or some thread that may block a lot of resources. Some other cases for thread dumps are a low number of certain threads like application threads or anything like that. I also use thread dumps in case of out of memory errors.

4) And last, but not least, is it normal for a full thread-dump to last 13

minutes ?

--> No, this is absolutely not normal.

Cheers,

Anja

[Former Member · Accepted solution]

Dear Anja,

thank you for your answer.

Meanwhile we have had confirmation that this was in fact caused by Core Dump (and not thread dump, as I initially mentioned).

SAP recommended us to switch off the Core Dump, by reconfiguring the -XDump parameter.

Kind Regards

/Ricardo