SAP Basis Learnings

1. Can problems with system replication impact the performance on the primary system ? 2. Is it supported to set up a replication scenario between systems with different hardware ?  Yes, it is possible to set up replication between systems that differ in terms of hardware (e.g. different manufacturer, different memory sizes, different number of CPUs). From a system replication perspective you only need to make sure that the number of hosts is identical on all sites and that every service has a partner on all sites.  3. Is it supported to set up a replication scenario between systems with a different SAP HANA patch level ?  It is allowed to use different SAP HANA patch levels in a replication scenario as long as the patch level of the replicated system is not lower than the patch level of the primary system. It is also allowed that the replicated system is on a higher SPS level than the primary system.  This possibility can be used for near-zero downtime upgrades (NZDU) upgrades

Basic troubleshooting process/steps follows as below. Database Starts: As on ABAP the first step is to check and start the database. No dedicated developer trace is created in the work directory as the database has its own logs. If the database does not start correctly, it should be visible within seconds and errors will be available within the DB logs. Developer traces: Refer to your DB logs. Startup: JSTART is called next, it takes the role of the Java instance controller which analyzes its configuration and initializes SAP signal handling and opens the control port. There is very rarely an issue with the initial load of JSTART. If for some reason this fails you most likely have a problem with your instance profile. Developer traces: dev_jstart Offline Deployment: The Java instance controller reads the instance definition and creates a child process that initializes JVM and starts the OFFLINE DEPLOYMENT program which performs the deployment steps in the Java database. In the ‘busine

AS Java Cluster Architecture An AS Java cluster consists of several types of instances, each one of which has an instance number and can be started,  stopped and monitored separately. They are 1.          Central services instance The central services instance consists of a Message Service and Enqueue Service . They are responsible for lock  administration, message exchange and load balancing within the Java cluster. 2.         One or more Java instances A Java instance consists of an Internet Communication Manager (ICM) and one or several server processes . The ICM  handles requests coming from clients and dispatches them to the available server processes , which actually process the requests. 3.         Database The database stores system and application data. There is one central database. It is also possible to have several  application databases. Minimum AS Java Cluster Installation: Large AS Java Cluster Installation: Java Instance: A Java instance is a unit in t