In SAP Quality Management's Statistical Process Control (SPC), the action limits (upper and lower) define the critical boundaries for process stability. When a measured value for an inspection characteristic falls outside these limits, it signifies a statistically significant deviation, indicating that the process is out of control. The system can be configured to automatically assign a 'reject' valuation to the inspection characteristic when an action limit is violated, as this is considered an unacceptable result.

A. Warning limit: Exceeding a warning limit indicates a potential process deviation and serves as an alert for closer monitoring, but it does not typically trigger an automatic rejection.

B. Moving average line: This is a trend line representing the average of several recent data points; it is used for analysis, not as a direct limit for rejecting an individual measurement.

C. Center line: The center line represents the process mean or target value. It is a central reference point, not a boundary for acceptance or rejection.

1. SAP S/4HANA Help Portal

Quality Management (QM)

"Valuation of a Characteristic with Control Charts": This official documentation states

"If a sample value lies outside the action limits

the system can automatically reject the sample. If a sample value lies between the warning and action limits

the system issues a warning." This directly supports that action limits are used for rejection.

2. SAP S/4HANA Help Portal

Quality Management (QM)

"Automatic Valuation for SPC Characteristics": This section details the valuation rules. It specifies that one of the rules for rejection is: "A sample is rejected if the mean value lies outside the action limits." This confirms the function of the action limit in the valuation process.

3. Montgomery

D. C. (2019). Introduction to Statistical Quality Control (8th ed.). Wiley. Chapter 6

"Control Charts for Variables

" explains that points plotting outside the control limits (commonly referred to as action limits in practice) are a primary signal of an out-of-control process requiring immediate investigation and corrective action

which in a manufacturing context often includes rejection of the associated item. (General principle supporting the SAP-specific implementation).