IntroductionThis unit introduces the DB2 Database Manager and the basic concepts behind a table.After completing this unit, you should be able to:
- Identify the advantages of a relational database
- Define a relation
- Name the language used to talk to a relational database manager (RDBM)
- List three characteristics assigned to each column
- Define the tasks performed by DB2 when running an application
- Define the roles that are performed within DB2
The ease of working with a relational databaseWe work with tables of data every day. An Excel spreadsheet usually consists of rows and columns. A phone book is another example of a table of data. Each page has the same columns (name, address, and phone number), just different rows. Phone books are in alphabetical sequence. The rows in a relational database may or may not be in a particular order. A relational database is a table database, consisting of rows and columns. At each juncture of a row and column, one and only one value may be present, according to relational theory.
Load data into a DBMSDatabase managers provide many services, such as:
- Logging – Saving “before” and “after” images (called UNDO and REDO records) of any DB2 rows changed by SQL (INSERT, UPDATE, DELETE).
- Security – Monitoring and controlling access to DB2 data
- Optimization – Minimizing the use of system resources (CPU cycles and physical I/O) when performing SQL queries and doing other DB2 work
- Locking – Serializing the access to DB2 data in order to allow concurrency, while guaranteeing data integrity
- Recovery – Restoring DB2 data due to outages, system failures or corruption by incorrect program logic
- Data integrity – Database theory demands that all changes to data follow the ACID model. From examples during this course, you will see that DB2 does apply the characteristics of this model: