WAT data, which is short for Wafer Acceptance Test data, refers to the data collected during the testing of individual wafers to check if they are acceptable against the specification of the process. PCM data refers to the data collected during the production process and stands for Process Control Monitor. This data is used to track and analyze production trends, identify sources of variability and to control the production process. WAT and PCM data can be used to identify and address yield issues early in the production process, therefore improving overall yield and reducing costs. Often WAT data and PCM data are the same data. There are other terms used for this data such as "eval" or "e-test" data.