AS ABAP Architecture
Architecture showing the interaction between ABAP processes in a SAP system with a central instance and 1 dialog instance. Note that there is no enqueue process within the dialog instance.
• The AS ABAP message server process is for internal communication. For example initiating updates , requesting/removing locks , triggering background requests etc. It keeps track of which instance is available by periodically pinging each instance.
• There is 1 dispatcher per instance. In a system with multiple instances , the dispatchers communicate with each other through the message server.
• All requests received through HTTP are handled by the ICM. Each ICM then forwards the request to the dispatcher within its own instance.
• The gateway process accepts requests that follow the RFC protocol. Typically such requests are sent from either other SAP systems or from applications running outside the SAP system.
AS ABAP Processes
• Dispatcher Work Process – 1 dispatcher work process per Application Instance and per each Dialog Instance. If there is 1 central Instance and 2 dialog instances in an SAP system , there will be 3 dispatchers. The role of the dispatcher is to distribute incoming requests to the ABAP worker threads.
• Dialog Work Process (D) – A minimum of 2 dialog work processes required per dispatcher that need to be configured per instance. This work process executes the transactions as required and communicates with the database instance processes
• Background Work Process (B) – Background work processes execute programs that run without interacting with the user. At least two background work processes for each SAP system are required. More than one background work process for each dispatcher can be configured.
• Enqueue Work Process (E) – Only 1 enqueue process exists in each SAP system. This process ensures that updates are serialized with the help of a lock table.
• Update Work Process (V) – Minimum 1 update process is required , and more than 1 process per dispatcher is allowed. This process takes care of processing update requests.
• Spool Work Process (S) – Minimum 1 spool process is required and more than 1 process per dispatcher is allowed. This process passes sequential data to output devices such as printers.
• Message Server (M) – Only 1 message server exists in the SAP system and is installed on the central services instance. It is responsible for communication between the different dispatchers of each SAP instance within the same SAP system.
• Gateway (G) – There is exactly 1 gateway Per Dispatcher in a SAP system.The gateway is meant to allow communication between different SAP systems.
• Internet Communication Manager – There is only 1 icm per SAP system.The ICM receives requests for HTTP protocol and forwards it to the ABAP dispatches for further processing.
Additional note:
• If an SAP system comprises of 1 central instance with number 01 , and 2 dialog instances , with number 02 and 03 , then the SAP system is said to be comprised of DVEBMGS01 , DVEBMGS02 and DVEBMGS03 instances.
• SAP uses the acronym DVEBMGSxx , where xx is the instance number to denote an SAP instance within the SAP system.
