If operational data is kept in the databases of the ERP -system, it can create a lot of problems. As time passes, the amount of data will increase and this will affect the performance of the ERP system. So it is better to archive the operational data once its use is over. When I say 'the use is over', it does not mean that the archived data is useless. On the contrary, it is one of the most valuable resources of the organization. However, once the op~rational use of the data is over, it should be removed from the operational databa~es. For example, one the financial year is over, the daily transactional data can be archived. Figure 5 shows what happens if the data is not archived.
It is evident from the Figure 5 that even though the operational data volume is nearly the same each year, since the data is not archived, the total amount of data that is stored in the operational database will go on increasing. Figure 6 shows the effect of keeping this huge amount of data in the operational database.

It is clear from the graph that as the volume of the data in the database increases, the performance of the database and the related applications decreases. "It is evident that we 'should separate the operational data from the non¬operational data. Here 'the term archive data is not used, because if the non operational data is archived, there is little or no use for it. But this data is a very valuable resource and is too precious to be kept in some archive. It is in this situation that a data warehouse comes in handy.Separating it from the data in operational systems can access the primary concept of data warehousing is that the data stored for business analysis most effectively. The most important reason for separating data for business analysis, from the operational data, has always been the potential performance since analysis processes much more complex and sophisticated. In addition to producing standard reports, today's data warehousing systems support very sophisticated online analysis, including multi-dimensional analysis