Integration of Data Sources

Question 1

What does ETL stand for?

Answer 1

Extract, Transformation, Loading

Question 2

What are some advantages of using flat files?

Answer 2

No overhead of maintaining data as DBMS does.
Sorting, merging, deleting, replacing and other data migration functions are much faster outside the DBMS.

Question 3

What are the disadvantages of using Flat Files?

Answer 3

1. No concept of updating.
2. Queries and random access lookups are not well supported by the system.
3. Flat files cannot be indexed for fast lookups.

Question 4

Name 4 purposes flat files should be used for?

Answer 4

1. Staging source data for safekeeping and recovery
2. Sorting data
3. Filtering
4. Replacing Text Strings

Question 5

What is Log Scraping?

Answer 5

Involves taking a snapshot of the database redo log at a certain time and finds the transactions affecting the tables that ETL is interested in.

Question 6

What is Log Sniffiing?

Answer 6

Involves pooling the redo log at small time granularity and capturing the transactions on the fly.

Question 7

What are the 4 basic steps needed for conceptual schema integration?

Answer 7

1. Pre-integration analysis
2. Comparison of schemas
3. Conformation of schemas
4. Merging and restructuring