19.5. BACKUP AND RECOVERY
You are aware of the backup and recovery procedures in OLTP systems. Some of you, as database administrators, must have been responsible for setting up the backups and probably been involved in one or two disaster recoveries.
In an OLTP mission-critical system, loss of data and downtime cannot be tolerated. Loss of data can produce serious consequences. In a system such as airlines reservations or online order-taking, downtime even for a short duration can cause losses in the millions of dollars.
How critical are these factors in a data warehouse environment? When an online order-taking system is down for recovery, you probably can survive for a few hours using manual fall-back procedures. If an airlines reservation system is down, there can be no such manual fall-back. How do these compare with the situation in the data warehouse? Is downtime critical? Can the users tolerate a small loss of data?
19.5.1. Why Back Up the Data Warehouse?
A data warehouse houses huge amounts of data that has taken years to gather and accumulate. The historical data may go back 10 or even up to 20 years. Before the data arrives at the data warehouse, you know that it has gone through an elaborate process of cleansing and transformation. Data in the warehouse represents an integrated, rich history of the enterprise. The users cannot afford to lose even a small part of the data that was so painstakingly put together. It is critical that you are able to recreate the data if ...