be stored in the form of raw data in a history server 100 in a manner split in terms of time into independent files for each measuring point without compressing the data a coding module 40 can be integrated in the history server 100 which coding module gradually compresses the raw data stored in the raw data format in a decoupled and individual manner as a result of which the raw data are converted into a compressed format in a parallel manner and independently of their actual archiving the coding module 40 interacts with a decoding module 50 which is likewise integrated in the history server 100 the decoding module 50 is provided for the purpose of unzipping the data compressed by the coding module 40 following a request from the process control system a display module 60 is provided which depicts a trend or a report for example with the unzipped data and further available data in the raw data format for further processing when reading the data from the coding module 40 for example in order to display a long term trend or a report the compressed or zipped data can be converted using the decoding module 50 and like.