on 10-24-2017 8:54 PM
Hello everyone,
I wonder how ENABLE/DISABLE automerge operation is implemented in SAP HANA.
The problem is that our systems (SP11/SP12) suffer from long running DISABLE/ENABLE auto merge regularly (time fluctuates between 20-120 sec).
Moreover, from time to time we face deadlocks by running this operation. Deadlocks which we can't explain since we see no other locks in the system.
Logically it should be just a turn on/turn off operation. But it appears there is something more going on the background.
I've run some tests with empty CDS-based and regular run-time tables.
What I noticed was:
So based on the described above, my questions are:
I'd highly appreciate it if anyone could shed some light on this.
Cheers
Elena
Lars, the fact you don't care is obvious. But in fact as a person who acts here as a SAP representative you should.
"As for the reason for using locks on catalog operations: how would you implement consistent catalog updates otherwise? Think two or more sessions changing that flag in parallel. In order to guarantee that, there needs to be some kind of locking mechanism - here, it is locks."
Still not a reason to check or lock dependent objects. As I said the implementation is development- and support-friendly but not customer-friendly in this specific case.
"that you don't even know how it is in fact implemented, had been implemented that specific way."
Exactly, that's why I came to this site with my question. I got your answer. The only difference is that I see the situation as someone who consumes a solution but you as someone who represents an owner of a solution. Represents in a quite aggressive way btw.
I can't provide logs here because of privacy. If I blur object names, it wouldn't make sense either. What I can say is that now I have more logs to support the idea it happens because of catalog locks. As I suspected and as you confirmed. I'll raise an incident for sure. But based on experience you gave me I am not sure this incident is to be resolved in a positive way.
PS So SAP representative claims that up to 120 sec for DISABLE AUTOMERGE because of excessive catalog locks is not something dramatic? LOL. For now the topic is closed. I'll return when I have some more info.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.
Lars, what kind of inconsistency could enable/disable automerge create? It seems you can't provide any example instead labelling my answers odd, finger pointing, DRAMA etc.
ok, I made conclusions.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.
Don't really care about your "conclusions", but you wrote about "dramatic" execution times and deadlocks without providing any substantiating material and you were the one coming up with why something, that you don't even know how it is in fact implemented, had been implemented that specific way.
As for the reason for using locks on catalog operations: how would you implement consistent catalog updates otherwise? Think two or more sessions changing that flag in parallel. In order to guarantee that, there needs to be some kind of locking mechanism - here, it is locks. I understand that this can be a difficult concept depending what environment one is used to, but locks are often used not so much to gain the option to change something, but to stop others from changing the same bit at the same time.
Now, you could of course go and say: yes, but the other sessions, that change the catalog, change something different. So, the lock is on the wrong level of granularity. Fair point, but choosing synchronisation points can be tricky and so far, your case is the first where this might be the problem. Maybe, the way you use this is different from most other users? Would that warrant a change in the software?
How about you follow up with a support incident and let the community know about the outcome? There's definitively and audience for that here.
User | Count |
---|---|
84 | |
10 | |
10 | |
9 | |
7 | |
6 | |
5 | |
5 | |
4 | |
4 |
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.