Database Reference
In-Depth Information
Copyright by SAP AG
Update Concept
The SAP update concept can be better understood by examining the SAP logical unit of
work (LUW) and database LUW. SAP LUW is a SAP transaction encompassing a business
process that could include several screens. Each screen's data commit will constitute a data-
base transaction or LUW. One SAP LUW may include several database LUWs.
When a screen commit is issued, the data is written to temporary update tables. The
entries are not yet written to the application tables. Each SAP transaction has a dialog and
an update component. The dialog component is executed by one or several dialog work pro-
cesses. The update component is executed by the update work processes. At the end of the
dialog part of the SAP transaction, the update part starts in the update work processes and
data is written from the update tables to the permanent application tables.
Updates are processed in three different ways, depending upon the priority. Priority 1 up-
dates are processed in time-critical U1 update work processes. One example of a priority 1
update is order creation. Priority 2 updates are processed in nontime-critical U2 update work
processes. One example of such an update is statistical data. The third category of updates is
referred to as a collective run. Collective run updates are collected and executed at a later
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