1 To complete the logon process, the presentation server connects with a dispatcher.
2 When the user tries to run a transaction, the user's request comes from the presentation server to the dispatcher and is put into the local wait queue.
3 When the dispatcher recognizes that a work process is available, the user's request is taken from the wait queue and sent to the work process
4 When a user is dispatched to a work process, "user context" data – the user's logon attributes, authorizations, and other relevant information – is transferred from the roll buffer, extended memory, or the roll file into the work process. This transfer (by copying or mapping, as appropriate) of user context data into work process memory is the mechanism known as a "roll in". Transaction processing then begins.
5 If data from the database is required to support transaction processing, a request for data is sent to the database interface, which in turn sends a request through the network to retrieve the information from the database.
6 When it receives the request, the database searches its shared memory buffers. If the data is found, it is sent back to the work process. If the data is not found, it is loaded from the disk into the shared memory buffers.
7 After being located, the data is taken from the shared memory buffers and sent back across the network to the requesting database interface. Transaction processing resumes.
8 Before accessing the database service, the database interface searches for the data in the R/3 buffers. If the data is found, it is relayed back to the work process where processing resumes. If the data is not found, the database interface sends a request over the network to retrieve the information from the database
9 If the data loaded from the database is eligible for R/3 buffering, it is placed in the R/3 buffers. Transaction processing resumes.
10 When transaction processing is completed, the dispatcher is notified of its completion. The results of the transaction are then sent back to the presentation server.
11 After the transaction finishes and the work process is no longer required, the user context data is rolled out of the work process.
12 CPU time is the amount of time during which a particular work process has active control of the central processing unit (CPU).