1. The System Catalog Describing the Data Copyright © Curt Hill 2003-2008
Describe the tables of metadata
Copyright © Curt Hill

2. What does a DBMS Store? Obviously: the data of the relations
Less obviously:
Relation formats
Field attributes
Index formats
Metadata: descriptions of how the data is stored
Copyright © Curt Hill

3. Table Metadata Table Name – used in SQL File name – internally used
Fields
Name
Type
Other attributes – such as unique
Index names on this table
Any contraints
Integrity
Referential
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4. Other Metadata Index Users View Name Structure type Names Passwords
B+Tree
Hash
Users
Names
Passwords
Authority
View
Description
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5. Statistics Statistical data may also be stored in the system catalog
This does not have to be updated at every change
Which could impede performance
Must be periodically updated
Data could include for either tables or indexes:
Size in terms of records and pages
Range and height for tree index
Copyright © Curt Hill

6. Storage The system catalog is merely a set of relations
Hence it is a database
Manipulated with normal means with some special privileges
Each DBMS may use different tables with different names
The login procedure then becomes a stored procedure
Take a user ID and password
Plug into a query
Find the security attributes
If there are none then the user is invalid
Copyright © Curt Hill