Work processes and its type

 In SAP Basis, work processes are the fundamental components of an SAP application server that execute the actual tasks and programs requested by users or background jobs. They are managed by the Dispatcher, which distributes incoming requests to available work processes of the appropriate type.

You can monitor work processes in transaction SM50 (or SM66 for a global overview across all application servers).

How Work Processes Function

When a request comes to an SAP application server:

1. Dispatcher: The dispatcher receives the request from the presentation layer (SAP GUI, web browser, etc.) or from other components.
2. Queue: The request is placed in a request queue.
3. Assignment: The dispatcher checks for an available work process of the required type.
4. Execution: Once assigned, the work process executes the program or transaction. This involves:
   • Screen Processor: Handles user interaction and screen flow logic.
   • ABAP Processor: Executes the ABAP code of the application program.
   • Database Interface: Communicates with the underlying database to read or write data.
   • Task Handler: Manages the overall execution of the request within the work process.
5. Release: After completing the task, the work process becomes available again for new requests.

Crucially, a single user's interaction (an SAP transaction) might involve multiple "dialog steps." The dispatcher can assign different dialog steps of the same transaction to different dialog work processes, a concept known as work process multiplexing. This significantly improves system throughput and responsiveness by not tying up one work process for the entire duration of a user's session.

Types of Work Processes

SAP systems typically have several types of work processes, each specialized for a particular kind of task:

1. Dialog Work Process (DIA)

   • Function: Handles interactive user requests, such as entering data in a transaction, navigating through screens, or executing reports in foreground.
   • Importance: These are critical for user experience and system responsiveness. A sufficient number of DIA WPs ensures smooth user interaction.
   • Profile Parameter: rdisp/wp_no_dia
   • Note: Every SAP application server must have at least two dialog work processes.

2. Update Work Process (UPD)

   • Function: Executes database update requests. These updates are typically triggered by a COMMIT WORK statement in a dialog work process. They ensure data consistency and integrity by applying changes to the database.
   • Importance: Essential for transactional data processing. If update processes are not functioning, data can become inconsistent, and business transactions might fail.
   • Profile Parameter: rdisp/wp_no_vb (for V1 updates)
   • Note: There can be two types of update processes:
     • V1 Updates (Critical Updates): Handled by UPD work processes (rdisp/wp_no_vb). These are high-priority, time-critical updates (e.g., financial postings).
     • V2 Updates (Less Critical/Deferred Updates): Handled by UP2 work processes (rdisp/wp_no_vb2). These are for less critical updates that can be processed with lower priority (e.g., statistics updates).

3. Background Work Process (BTC)

   • Function: Executes background jobs (batch jobs). These are typically long-running, resource-intensive tasks that do not require immediate user interaction, such as report generation, data archiving, or mass processing.
   • Importance: Enables automation of routine tasks and allows resource-intensive operations to run outside of peak user hours.
   • Profile Parameter: rdisp/wp_no_btc
   • Note: At least two background work processes are usually recommended per SAP system.

4. Enqueue Work Process (ENQ)

   • Function: Manages logical locks on database objects and shared memory. It ensures data consistency by preventing multiple users or processes from simultaneously modifying the same data. It administers the lock table in the shared memory.
   • Importance: Crucial for data integrity in a multi-user environment. Without it, data conflicts and inconsistencies would be rampant.
   • Profile Parameter: rdisp/wp_no_enq
   • Note: In an ABAP system, there should be only one enqueue work process. This work process typically resides on the SAP Central Services (ASCS) instance.

5. Spool Work Process (SPO)

   • Function: Manages print requests and passes sequential data streams to output devices (printers, fax devices, optical archiving).
   • Importance: Handles all printing and output management for the SAP system.
   • Profile Parameter: rdisp/wp_no_spo
   • Note: At least one spool work process is required in the entire ABAP system.

Other Important Processes (Not strictly "Work Processes" but related to SAP system operation):

While the above are the primary "work processes" that execute tasks, an SAP application server instance also contains other vital components:

• Dispatcher (DP): The central process that manages the work processes, distributes requests, and handles communication with the SAP GUI and other components. It's the "traffic controller" of the application server.
• Message Server (MS): This is a key component of the Central Services (ASCS) instance. Its primary role is to handle communication between different application servers within the same SAP system (load balancing, message exchange) and to provide information about the system landscape.
• Gateway Process (GW): Also typically part of the ASCS instance. It enables communication between SAP systems (via RFC - Remote Function Call) and between SAP systems and external systems.

Configuration and Monitoring

• Configuration: The number of each type of work process is configured using profile parameters in the SAP instance profile (maintained via transaction RZ10). Changes to these parameters usually require a restart of the application server to take effect.
  • rdisp/wp_no_dia
  • rdisp/wp_no_vb
  • rdisp/wp_no_vb2
  • rdisp/wp_no_btc
  • rdisp/wp_no_enq
  • rdisp/wp_no_spo
  • rdisp/wp_max_no: Defines the maximum total number of work processes.
  • rdisp/max_wprun_time: Max runtime for a dialog work process before it's canceled.
• Monitoring: Use transaction SM50 to see a real-time overview of all work processes on a specific application server. SM66 gives a global overview across all application servers. This allows Basis administrators to identify issues like long-running processes, processes in a "stopped" or "PRIV" status, or bottlenecks.
• Dynamic Work Processes: SAP systems can also start "dynamic" work processes (typically dialog or update) if all configured work processes of a certain type are busy. This provides flexibility and helps handle temporary load spikes. The parameter rdisp/wp_no_restricted can be used to configure "stand-by" work processes.

Understanding work processes is fundamental for SAP Basis administrators to effectively monitor system performance, troubleshoot issues, and optimize resource utilization within an SAP landscape.