Java AS Architecture
Central instance in a Java AS is the instance in which SDM (Software Deployment Manager) resides. Central services instance of an AS Java has Message Serverand Enqueue service. All other instances are dialog instances.
In a Java AS, Central services instance interact with Central instance and Dialog instance. Message server present in it is responsible for load balancing amongst different instances and has the status of all the instances. Each instance can directly interact with Enqueue service which holds the logical locks.
|Java AS Architecture|
Since over here both the ABAP and JAVA instance can receive communications through browser, so ICM(Internet Communication Manager) decides here which instance to call. For example, if there is a call for an ABAP Web Dynpro through browser then ICM will forward the request to ABAP dispatcher and if there is a call for JSP (Java server Page) then ICM will transfer the request to Java dispatcher.
Also the Database schemas for ABAP and Java instances are different for ABAP+JAVA AS. Work processes can only access ABAP data and server processes can only access JAVA data. But for the data exchanges between the two schemas we have JAVA Connector (JCo). This connection is needed to display the data of ABAP AS in JAVA AS. The SAP JCo is integrated into the AS Java and is also used when an AS Java system has to communicate with a remote AS ABAP system.
This was continuation for the previous article. Types of SAP NetWeaver Application Server