Database Reference
In-Depth Information
Rule:
One gateway for each SAP instance.
Data Flow in a NW AS ABAP
SAP NW AS ABAP provides the technology for running ABAP applications. Select Java
applications can now be run in the same ABAP work process with the new Virtual Memory
Container (VMC) technology.
Data flow in a typical NW AS ABAP system (see
Figures 2-2
and
2-3
) for a SAPGUI re-
quest is as follows:
1. The end user will log in to the desired SAP system from SAPGUI.
2. Logon groups defined in the system will connect to the message server and, based on
theloaddistribution,willdirecttherequesttotheappropriatedispatcher.Oncetheuser
is assigned to a dispatcher, the user remains with the same dispatcher until logged out.
3.Thedispatcherwillpickuptherequestanddistributeittotheworkprocess.Ifthework
processes are all occupied, then they are gathered in a queue.
4. The work process executes ABAP or SAP-delivered select Java programs via VMC
technology in the ABAP engine (see the section “VMC Technology”).
5. If needed, the work process will connect to the underlying relational database via a
database interface using Open SQL.
6. The database interface converts Open SQL to native SQL through the underlying rela-
tional database and gets the requested data.
7. The data is sent back to the end user.
VMC Technology
SAP has developed a new Java VMC architecture and integrated it with the ABAP work
process for the purpose of executing SAP-developed Java programs. This is not intended for
executing custom-developed Java programs. In such a case, customers are advised to use the
SAP NW AS Java.
The SAP VMC architecture (
Figure 2-4
) allows an ABAP work process to use a pool of
Java virtual machine from a preallocated virtual machine pool. VMC is already coded in the
SAP standard kernel. However, it is not activated by default, and the following profile para-
meters need to be activated and configured to use the VMC in NW AS ABAP-based sys-
tems.
