Temp-Tables and ProDatasets are a key construct of many ABL applications – with or without the Progress AppServer. As a fundamental data structure, they allow to separate the gathering of information and it’s processing. At first sight Temp-Table and ProDatasets can be passed very easily as parameters. However, there are some culprits causing common mistakes in the use. In this presentation we will highlight potential issues and how to detect and fix them and discuss potential performance issues when using Temp-Tables and ProDatasets.