For example, an alert can be set to proactively reorganize a database when it reaches its storage capacity. And other tools exist that can ease the burden of performance management and analysis. But many of the supposedly proactive steps taken against completed applications in production are truly mostly reactive. You need a firm definition of database performance before you can learn ways to plan for efficiency. Think, for a moment, of database performance using the familiar concepts of supply and demand.
Users demand information from the database.
The DBMS supplies information to those requesting it. The workload that is requested of the DBMS defines the demand. It is a combination of online transactions, batch jobs, ad hoc queries, data warehousing analysis, and system commands directed through the system at any given time. Workload can fluctuate drastically from day to day, hour to hour, and even minute to minute. The overall workload has a major impact on database performance.