Central Instance & Dialog Instance Differences

[Former Member]

Hello All,

Is there any difference between Central Instance & Dialog Instance if it is AS ABAP System??For dual stack & AS Java I have no doubt(In SCS MS & ES resides) for AS ABAP System I am in a little bit doubt.

[former_member185327]

Hi, Although it is an old thread, but still I am sharing what I know. For ABAP System The Central Instance is distinguished from other instances is that fact that it contains the Enqueue Server and the Message Server. All other instances which contains other work process like dialog, update, spool can be called as dialog instance. The Central Instance communicate with the Dialog Instance usually through the Message dispatcher via ABAP Dispatcher Thanks and Regards Anurag Das

[Former Member]

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[former_member183044]

Hi Das,

The major difference between Central instance & Dialog Instance is that Central Instance contains Message Server & Dialog Instance doesn't contains Meassage Server.

Regards

Praveen

[Former Member]

The difference between CI and DI related to workprocess is that the dialog instance will not have a message server and enque work process but the dialog instance do not have these things in it. And as per the use of dialog work process we can add the work process into dialog instance.

[Former Member]

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[Former Member]

Solved.

[sunny_pahuja2]

Hi,

Yes, central instance and dialog instance are totally different. Dialog instance is used for load balancing. By default when you install an SAP system, central instance will be installed. If later on because of system load, you can install a dialog instance for load sharing.

Thanks

Sunny

[Former Member]

Sunny I also know that DI is used for load balancing..But from the OS file system structure whether there is any difference??If CI fails whether DI will work??

[Former Member]

Hi,

Please be informed that the DI will not work if the CI is down at the OS level. This is because the DI shares the executables with the CI (sapmnt directory) at the OS level.

Also the message server service runs in the CI and hence if the SAP in the CI stops working for some reasons, the DI will not be able to connect to the database instance as the message server service is down.

Regards,

Varadharajan M

[Former Member]

HI,

A Central Instance provides SAP services for the SAP Web AS ABAP or the SAP Web AS JAVA Add-in variant. These services consist of SAP work processes such as dialog, update, batch, spool, gateway, Message Server and the Enqueue Server. It does not include the database processes.

Dialog Instance or sometimes called Application Server is a SAP instance, without the DB instance, consisting of a dispatcher process and dialog work processes. A dialog instance does not contain the system-critical enqueue and message service components.

Br

GYaan

[Former Member]

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