Database Reference
In-Depth Information
SAP JVM
SAP is using its own JVM, referred to as SAP JVM. SAP JVM is a Java SE 5-compliant
virtual machine based on Sun's HotSpot Technology.
Robust Java Architecture
Because of the FCA, better use of shared memory to keep pending user request queues, ICM
redirection capabilities, and SAP JVM, the overall robustness of the SAP NW AS Java plat-
form has improved significantly. This should translate into a stable and reliable platform for
customers using SAP Java business applications.
Now that we have looked into the detailed architecture of the SAP NW AS Java, let us
study the practical aspects of starting the SAP Java stack and also examine the internals of
the startup process. This understanding will help us to troubleshoot any startup problems
and quickly resolve the issues.
Starting a SAP NW AS Java System
Login as <sid>adm user (e.g., devadm for the SAP system where SAP SID=DEV) and issue
the startsap command in the user's home directory. This will start the SAP NW AS Java sys-
tem. There is a specific sequence in which the startsap script will start the system, which is
explained in the next section.
Start and Shutdown Sequence
SAP Java-based systems will start in the following sequence:
1. Database is started.
2. Central services instance is started (Java message server and enqueue server).
3. Central instance is started (Java dispatcher, server process, and SDM).
4. Dialog instances are started (Java dispatcher and server process).
The shutdown sequence is the exact opposite of the startup sequence.
When the startsap command is issued, it will start the Java startup and control frame-
work. It is the responsibility of the startup and control framework to start the rest of the
components and processes of the SAP Java cluster. The startup and control framework is a
little different in NW 7.0 and NW 7.1 releases. We will study both here.
