RAC or cluster issue

[Former Member]

Hello

I am pritty new in this area but anyway. We have a customer running ECC5 on Oracle on RAC(2 database server forming RAC).

As I am short in time (and also not an Oracle guy) I would ask you is it normal (I can see this in running wmstat command(on tru64) a node is almost on 100% of CPU usage while other is almost idle.

Is this normal behaviour?

If not what could be the reason (each node is on other location)?

Is this Oracle issue or could be some other (SAP oriented issue) ?

Interesting aslo that when logging to ECC5 I can not see in sm51 database server(s). How can this happen? Maybe because of RAC(sorry RAC is completely something new for me)

I am trying to find answers desperately to this questions but I do not find them.

Thank you in advance for any help

[Former Member · Accepted solution]

Whilst RAC is supposed to be a Oracle architecture where one db node is in the active mode & the other is in the standby node.

So it is normal you wont find anything actually happening on the standby server.

On you db active server however 100% CPU usage is not normal a well tuned system should have average 60% CPU utilization. But do you see a 100% CPU utilization always or is it just intermittent spikes?

If it is intermittent there is probably not much to worry but if it happens always it not at all an optimal configuration. Check which processes are being used, what is the I/O, is the CPU waiting on something, etc.

On the other question SM51 shows the hosts for SAP Application Servers (Dialog Instances) so if the host on which you have the database installed also has a SAP Application Server installed you'll see it in SM51 but if it only has a database instance running there you wont see it.

- Regards, Dibya

[Former Member · Accepted solution]

@Dibya: i saw some good replies from you so far, but i don't like this one a lot, sorry

Whilst RAC is supposed to be a Oracle architecture where one db node is in the active mode & the other is in the standby node.

RAC is THE architecture where all nodes are active at the same time. Standby database is a completely different functionality, although RAC and standby db can be used together.

@jan: there could be various reasons for one node to have high cpu usage, while others are idle. You will need to understand how your system is setup. So far we only know there are two RAC nodes. Still you will need to check if the database runs on both nodes, you can use the crs_stat command to check which resources are running where.

Second you need to investigate how SAP connects to the existing oracle instances (say RAC node), it is possible to connect a SAP instance to only one RAC node. Or you can use load balancing/failover over all nodes. This can be seen in the tnsnames.ora files.

Cheers Michael