More instances Vs More processes

[Former Member]

Hello All,

Recently we are facing a sporadic RFC problem on our produiction system. When the problem occurs, all the dialog processes are taken and we have system hang situation. After noticing this problem, we are noe in the processes of limiting the number of processes for RFC using the profile parameters. After this change only half of the dialog processes will be taken and half will be left for the users. To avoid the problem further, I'm thinking of adding additional Dialog instnace and using that specifically for RFC's. We have Application servers with 16 GB mem and 8 CPU's each. The load average on these servers is pretty low, about 1 %. Meaning we have plenty of resorces available on this server. Now my question is, is it a smart thing to just add more dialog processes to the existing application servers, or to create an additional instance on existing servers, to use specifically for RFC's ? Please advise.

Thanks,

Saritha

[tim_buchholz]

Dear Saritha,

this is hard to tell without a lot more details about what you are trying to do. It seems that at some point in time, more RFC load is generated than the system can handle concurrently. What is worse, is that you seem to do nested RFC calls meaning that an RFC will be issued from within an RFC which can mean that a dialog work process will be blocked and another free dialog work process will be needed to free up the first dialog work process. Unless you can give an upper bound on the number of concurrently active RFC calls, you will not succeed in making sure that you do not bring the system to a standstill.

Generally speaking, it is far more efficient to increase the number of work processes in one instance, as you do not have to replicate things like program and database buffers and the like. These will already be there in an existing instance, but will have to be considered if setting up a separate instance on another server.

However, having a dedicated instance to handle RFC load might be a good idea to ensure overall system availability.

Best Regards,

Tim

[Former Member]

Hello Tim,

Thank you for the reply.

I do understand that each instance has it's own buffer areas and a higher demand will be placed on the Physical Memory and other resources if we create additional instance on the same server. My question is, with a server, with low load average, is it still a good idea not to create additional instances, if there is a need. If the answer is yes, are we not wasting the resources on the server if the load average is very low and more than 75% of the system resources are idle most of the time? Please advise.

Thank you.

Best Regards,

Saritha.

[tim_buchholz]

Dear Saritha,

that is the crucial point, we are not having a problem with the streets in the night time, but during rush-hour. You can not judge this by looking at the average load on the system, but you will have to make sure that at all times the load can be handled.

Best Regards,

Tim

[former_member185954]

Hi Saritha,

Some more information is needed to provide a suggestion.

Can you please post what is the sizing of your Central instance and how much dialog processes are configured on it.

It would be also helpful to know which parameter you have changed.

Also let us know what kind of SAP are you running..for example whether it has ITS connected to it etc..

Regards,

Siddhesh

[Former Member]

Hi,

each additional work process take around 75-150MB of space and also we cannot increase more than more than 75+ dialog work process

adding additional instance is advisable if you have more resouces, in your case you can add additional instance.

Samrat

[Former Member]

Hello Saritha,

I will suggest you to have exclusive instance for the RFC and as you have a high end server you can afford also. Because of this the RFC connections will not bother the end users.

Do revert if you need any more info on this.

Best Regards,

Sachin.