1. A method for monitoring system performance of an in-memory computer system comprising operating one or more data processing units to perform steps of: conducting a plurality of on-line transaction processes (OLTPs) to receive and store data in a main memory component of the in-memory computer system; conducting a plurality of on-line analytical processes (OLAPs) on the data stored in the memory component to produce a plurality of data analysis results; storing the data analysis results in the main memory component; storing runtime information in a plurality of system tables in the main memory component relating to the step of conducting a plurality of OLTPs and the step of conducting a plurality of OLAPs; retrieving as monitoring data some of the information stored in the system tables; and performing one or more predetermined data analyses on the monitoring data to produce a plurality of system performance metrics.