SAP Work Process and Types

Work Processes

The SAP work process is a component of the application server that executes an ABAP application.
SAP work processes are started as operating system processes, each with its own process ID (PID).
The majority of the processing of the application is performed by the SAP work processes.

D – Dialog
V – Update
E – Enqueue
B – Background
M – Message Server
S – Spool
G – Gateway Server

Dialogue

It is the only work process which communicates interactively with the users.
There should be at least 2 Dialogue work process per instance. Dialogue work process initiates Update, Background and Spool.The dialog work processes are in charge of the interactive tasks of the R/3 system. A dialog work process performs the dispatcher in the request queues after user input are assigned to the next free work process. The dialog work processes execute just one single dialog step at a time and become immediately free for the next user request (dialog step), which is assigned by the dispatcher. This is called work process multiplexing. This means that the dialog work processes can be constantly switching between different user sessions. This type of processing allows a great deal of resource distribution; otherwise the system would need as many dialog work processes as the number of expected interactive users.  It works exactly the same as multiuser operating systems. Depending on the type of business transactions the users are working on, a dialog work process can support from 5 to more than 10 simultaneous users each. This means that 10 dialog work processescould theoretically support approximately 100 users. However, this is just a rule of thumb. Tuning this parameter means that if users have to wait long to get a free work process, you should increase the parameter.

Update

It is used to update the transactions in the database. It is initiated by Dialogue process. There should be at least 1 Update work process in the entire system. It is also recommended to have an update process for every 5 Dialogue.

Enqueue

It is used to provide locks for the records that are going to be updated. It ensures consistency for updates. There will be only 1 Enqueue configured in the system during the installation. It is possible to have more than one enqueue provided they are installed or configured on the central instance.

Background

The tasks which are expensive or time consuming are scheduled to run in the background mode noninteractively. There should be at least 2 background work process in the system

Message

There should be only 1 message server in me entire R/3 system. It is used to manage all the dispatchers. It is used to load balance the requests to identity the least loaded dispatcher. It is also used to provide locks to the request that are coming from Dialogue instances.
Gateway

It is used to provide a means of communication with SAP and NON-SAP systems. There will be only 1 gateway for each instance.

Spool

It is used to print the documents to a printer or output to a fax machine etc. There should be at least 1 Spool process in the entire system. It is also possible to configure more spool process depending on the print/spool volume.